79,887 results
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2. Liquid Wicking in a Paper Strip: An Experimental and Numerical Study
- Author
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Subhashis Patari and Pallab Sinha Mahapatra
- Subjects
Work (thermodynamics) ,Filter paper ,Capillary action ,General Chemical Engineering ,Microfluidics ,Evaporation ,General Chemistry ,Mechanics ,Article ,Chemistry ,Porous medium ,Water content ,Scaling ,QD1-999 - Abstract
In this decade, paper-based microfluidics has gained more interest in the research due to the vast applications in medical diagnosis, environmental monitoring, food safety analysis, etc. In this work, we presented a set of experiments to understand the physics of the capillary flow phenomenon through paper strips. Here, using the wicking phenomenon of the liquid in porous media, experimentally, we find out the capillary height of the liquid in filter paper at different time intervals. It was found that the Lucas-Washburn (L-W) model, as well as the evaporation model, fails to predict the capillary rise accurately. However, the detailed numerical solution shows a better similarity with the experimental results. We have also shown the different regimes of the wicking phenomenon using scaling analysis of the modified L-W model. The capillary rise method was applied to detect the added water content in milk. We used milk as a liquid food and found the added water content from the change in the capillary height at different concentrations of milk. Finally, results obtained from the paper-based device were verified with the commercially available lactometer data.
- Published
- 2020
3. The Study of Paper Capillarity with a Simple Technique
- Author
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Septia Ardiani, Handika Dany Rahmayanti, and Nurul Akmalia
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Absorption of water ,Materials science ,Absorption time ,Capillary action ,Simple (abstract algebra) ,visual_art ,visual_art.visual_art_medium ,cardboard ,Mechanics ,Absorption (electromagnetic radiation) ,Tissue paper ,Physical quantity - Abstract
The study of water absorption by capillarity on paper with a simple technique is simple but important to do to inform the public about the characteristics of paper and for the development of research on the absorption of different types of paper. In this study, five types of paper were used, namely HVS paper, cardboard, tissue paper, concord paper and buffalo paper. In the capillary water absorption test on paper, the physical quantities analyzed are the water absorption, the absorption time and the water absorption rate. The capillarity of the paper is a comparison of the rate of water absorption by the paper which is analyzed using the straight line movement approach. The value of water absorption is estimated using the ratio between the height of water absorption and the time absorption. Based on the results of the capillary test on paper, it was found that the water absorption height for the five types of paper increases with increasing absorption time. The highest water absorption capacity is tissue paper, which is 7.4 ± 0.2 cm every 180 seconds. While the lowest water absorption capillarity is HVS paper which is 0.5 ± 0.1 cm at the 180th second. Cardstock and buffalo paper have almost the same water absorption value and are higher than HVS paper and match. The absorption speed which is almost the same between cardboard and buffalo paper is due to the fact that both belong to the same type of paper, namely printing paper.
- Published
- 2020
4. Modeling the effect of creep in paper fibres under the influence of external loading and changes in moisture
- Author
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P. Samantray, Marc G.D. Geers, Ron H. J. Peerlings, Thierry Massart, Mechanics of Materials, Group Peerlings, and EAISI Foundational
- Subjects
Paper ,Work (thermodynamics) ,Résistance et comportement des matériaux ,Materials science ,Moisture ,Scale (ratio) ,Hygro-mechanics ,Mechanics ,Creep ,Microstructure ,Sciences de l'ingénieur ,Power law ,Technologie matières ligneuses ,Mechanics of Materials ,Fibrous network ,Stress relaxation ,Connaissance des matériaux ,Relaxation (physics) ,Déformation, rupture matériaux ,General Materials Science ,Instrumentation - Abstract
Paper is a material exhibiting a complex microstructure that is composed of a network of fibres at the micro-level. When subjected to external loading or variations in moisture conditions over different time scales, changes in strain that are non-linear with respect to time are observed at the sheet level (macro-scale). In order to investigate this time-dependent behavior of paper, a creep power law model is implemented within a finite element approach at the level of single fibres. This rate-dependent model is found to capture experimental results available in literature for single fibres with a good agreement (both quantitatively and qualitatively). Based on the identified model at the level of single fibres, the time-dependent hygro-mechanical response is upscaled towards the network scale. To this end, random model networks of ribbon shaped fibres are generated and their response is simulated. The network-scale response, emerging from the rate-dependent fibre model, demonstrates the ability to predict the response of networks subjected to relaxation at a constant moisture level. The developed numerical model predicts lower values of overall stress response in single fibres as compared to networks. Also, stress relaxation predicted by the rate-dependent model in the cross-direction of the networks is in agreement with the experimental observations. Therefore, one of the remarkable findings of the present work is that the developed rate-dependent model is robust enough to capture the sheet scale response also qualitatively. Based on the study of these computational results, a better understanding is achieved regarding the influence of mechanical and rate-dependent properties of single fibres on the hygro-expansion of complete fibre networks, and in particular of paper sheets., info:eu-repo/semantics/published
- Published
- 2021
5. Application of Cole–Cole model to transformer oil‐paper insulation considering distributed dielectric relaxation
- Author
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Sivaji Chakravorti, Biswendu Chatterjee, S. K. Ojha, and Prithwiraj Purkait
- Subjects
transformer oil-paper insulation ,dielectric testing techniques ,Materials science ,Transformer oil ,power transformer insulation ,lcsh:QC501-721 ,Energy Engineering and Power Technology ,Dielectric ,dielectric relaxation ,frequency domain ,Dielectric withstand test ,cable insulating oil ,law.invention ,ionic liquids ,oil-paper insulated transformers ,law ,elementary Debye relaxation properties ,lcsh:Electricity ,Cole–Cole diagram ,Time domain ,Electrical and Electronic Engineering ,time domain dielectric response ,Transformer ,transformer oil ,distributed dielectric relaxation ,paper ,dielectric mixtures ,Mechanics ,distribution density functions ,many-body interaction process ,Cole–Cole model ,polar liquids ,Nonlinear Sciences::Exactly Solvable and Integrable Systems ,Frequency domain ,dielectric materials ,insulation condition assessment ,Cole–Cole plots ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,lcsh:TK1-9971 ,Cole–Cole equation ,Test data - Abstract
Researchers have been exploring dielectric testing techniques both in time and frequency domain for insulation condition assessment of oil-paper insulated transformers. In a practical dielectric system, dipoles are found to behave according to a distribution of elementary Debye relaxation properties. Suitable distribution density functions have been proposed to characterise such many-body interaction processes. Cole–Cole diagrams can be one of the methods for studying the nature of frequency dependency of dielectric materials of complex structure. Cole–Cole plots are commonly used for characterising different materials such as dielectric mixtures, ionic liquids, cable insulating oil, polar liquids etc. The scope of its application for assessing transformer oil-paper insulation considering distributed relaxation process has not been explored yet. The present contribution discusses mathematical formulations used for transforming the experimentally obtained time domain dielectric response test data to distribution domain and further to frequency domain for obtaining the Cole–Cole plots. Findings about the influence of various operating conditions and insulation status on the Cole–Cole diagram have been reported in this contribution. Results of tests on field transformers are also presented. This paper attempts to employ the features of Cole–Cole diagrams as potential indicators for analysing condition of the oil-paper insulation considering distributed relaxation process.
- Published
- 2019
6. IMPROVING THE QUALITY OF MONITORING OF CIRCULATING AND WASTE WATERS OF PULP AND PAPER PRODUCTION
- Author
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Михаил (Mikhail) Семенович (Semenovich) Лурье (Lur'e), Юрий (Iuriy) Давыдович (Davydovich) Алашкевич (Alashkevich), Александр (Aleksandr) Владимирович (Vladimirovich) Смородько (Smorod'ko), and Ольга (Ol'ga) Михайловна (Mikhaylovna) Лурье (Lur'e)
- Subjects
погрешности монтажа ,Materials science ,installation errors ,Plant Science ,engineering.material ,vortex flowmeters ,Flow measurement ,sewage and circulating water ,Biomaterials ,symbols.namesake ,вихревые расходомеры ,Deflection (engineering) ,численное моделирование ,Measurement method ,Pulp (paper) ,Organic Chemistry ,flow body ,Paper production ,Mechanics ,Frequency spectrum ,Volumetric flow rate ,сточные и оборотные воды ,numerical simulation ,тело обтекания ,engineering ,symbols ,Strouhal number - Abstract
The issue of operation of submersible vortex flowmeters used in the systems of monitoring of circulating and waste waters of pulp and paper production is considered. It is shown that in the event of an error in the installation of these instruments, an additional error appears due to the angle between the axis of the flow body (TO) of the flowmeter and the axis of the pipeline. This error is related to the measurement method, which in turn leads to a change in the Strouhal number (Sh). The influence of this error leads to a change in the geometry of the flow part of the submerged flowmeter (the appearance of the angle β), which in turn leads to a change in the vortex formation process. Variants of finding this error are considered, from which the method of numerical modeling of hydrodynamic processes with subsequent processing by the method of experiment planning was chosen. For each investigated velocity of the fiber suspension and the angle of deflection of the TO axis, a graph of the frequency spectrum of the vortex formation process was obtained. Which was later used to find the number Sh. The dependence of the installation error ΔSh,% is presented. in the form of a response surface. It is revealed that the error in the installation of the TO, which is estimated by the angle β, is relatively small and varies linearly with increasing β. If the angle β = ± 3 ° is accepted as an allowable value, then the error in measuring the flow rate of the suspension will not exceed 0.25% over the entire range of velocities under consideration., Рассматривается вопрос особенностей эксплуатации погружных вихревых расходомеров, применяемых в системах мониторинга оборотных и сточных вод целлюлозно-бумажного производства. Показано, что при ошибке монтажа данных приборов может появляться дополнительная погрешность, появляющаяся вследствие угла между осью тело обтекания (ТО) расходомера и осью трубопровода. Данная погрешность связана с методом измерения, которая в свою очередь ведет к изменению числа Струхаля (Sh). Влияние данной погрешности приводит к изменению геометрии проточной части погружного расходомера (появление угла β), что способствует изменению процесса вихреобразования. Рассмотрены варианты нахождения данной погрешности из которых был выбран метод численного моделирования гидродинамических процессов с последующей обработкой методом планирования эксперимента. Для каждой исследуемой скорости волокнистой суспензии и угле отклонения оси ТО был получен график частотного спектра процесса вихреобразования на ТО, который впоследствии использовался для нахождения числа Sh. Представлена зависимость погрешности монтажа ΔSh,% в виде поверхности отклика. Выявлено, что погрешность монтажа ТО, которая оценивается углом β, является относительно небольшой иизменяется сувеличением β линейно. Если принять в качестве допустимой величины угла β=±3°, то погрешность измерения расхода суспензии не будет превосходить 0,25% во всем диапазоне рассматриваемых скоростей.
- Published
- 2018
7. Crack growth and energy dissipation in paper
- Author
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Juha Koivisto, Tero Mäkinen, Mikko J. Alava, Markus Ovaska, Maryam Hanifpour, Complex Systems and Materials, Department of Applied Physics, Aalto-yliopisto, and Aalto University
- Subjects
Digital image correlation ,Multidisciplinary ,Materials science ,Nonlinear phenomena ,lcsh:R ,lcsh:Medicine ,Hot spot (veterinary medicine) ,02 engineering and technology ,Mechanics ,Dissipation ,021001 nanoscience & nanotechnology ,01 natural sciences ,Article ,law.invention ,law ,Intermittency ,0103 physical sciences ,Paper sample ,lcsh:Q ,Fracture process ,010306 general physics ,0210 nano-technology ,lcsh:Science - Abstract
Here, we follow the stable propagation of a roughening crack using simultaneously Digital Image Correlation and Infra-Red imaging. In a quasi-two-dimensional paper sample, the crack tip and ahead of that the fracture process zone follow the slowly, diffusively moving “hot spot” ahead of the tip. This also holds when the crack starts to roughen during propagation. The well-established intermittency of the crack advancement and the roughening of the crack in paper are thus subject to the dissipation and decohesion in the hot spot zone. They are therefore not only a result of the depinning of the crack in a heterogeneous material.
- Published
- 2018
8. Effect of multi‐factors on heterocharges for oil‐impregnated paper in converter transformer using modified charge transport model
- Author
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Heng Zhang, Jiefeng Liu, Shen Yan, Xianhao Fan, Yiyi Zhang, and Mingchen Shi
- Subjects
TK1001-1841 ,Materials science ,Computer simulation ,Distribution or transmission of electric power ,Energy Engineering and Power Technology ,Mechanics ,TK3001-3521 ,Conductivity ,Space charge ,law.invention ,Dynamic simulation ,Temperature gradient ,Production of electric energy or power. Powerplants. Central stations ,Control and Systems Engineering ,law ,Insulation system ,Electric field ,Electrical and Electronic Engineering ,Transformer - Abstract
The heterocharge accumulated in the oil‐paper insulation system of the converter transformer will enhance the local electric field and cause insulation deterioration. Numerical simulation is an effective method to analyze heterocharge. Currently, the numerical simulation of heterocharge is mainly based on the bipolar charge transport (BCT) model and the impurity ion transport (IIT) model. However, the effects of temperature, conductivity, and thickness of oil‐impregnated paper on charge transport have not been considered in these models. In view of this, a modified charge transport (MCT) model by introducing the Maxwell–Wagner model and heat conduction equation is proposed in this paper based on the BCT model and IIT model. Then, the influence of multi‐factors (temperature gradient, moisture content, and oil‐impregnated paper thickness) on heterocharge accumulation is investigated by using the MCT model. The simulation results obtained by the MCT model are more consistent with the experimental results than the BCT model, which proves the accuracy and superiority of the MCT model. Moreover, the increase in temperature gradient, moisture content, and oil‐impregnated paper thickness will enlarge the ion dissociation rate, conductivity, and trap density, and thus promote the generation of heterocharge. In that respect, the MCT model is expected to optimize the insulation design and provide a reference for space charge dynamic simulation.
- Published
- 2021
9. BREAKDOWN VOLTAGE OF MICRON RANGE AIR INCLUSIONS IN CAPACITOR PAPER
- Author
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O. O. Palchykov
- Subjects
Permittivity ,Materials science ,электрический пробой ,модель конденсаторной бумаги ,микронный промежуток ,электростатическое поле ,метод конечных элементов ,finite element method ,Electrical breakdown ,electrostatic field ,Mechanics ,Finite element method ,TK1-9971 ,law.invention ,electrical breakdown ,model of capacitor paper ,micron gap ,Capacitor ,Volume (thermodynamics) ,law ,621.3.048.8 ,Electric field ,Breakdown voltage ,Electrical engineering. Electronics. Nuclear engineering ,Intensity (heat transfer) - Abstract
Purpose. To substantiate the breakdown mechanism of capacitor paper on the basis of numerical-field models with segmented cross-sections of cylindrical volumes of air and water, and also use the proposed models to determine the breakdown strength of air in micron-sized gaps under normal conditions. Methodology. The model bases on a finite element solution to an electrostatic problem in a volume of capacitor paper consisting of cellulose and pores with air and water. First, the possible scenarios for the growth of breakdown in capacitor paper are analyzed and to the conclusion is made, that complete breakdown developed from a partial breakdown in the air cavity. A brand of capacitor paper is chosen in such a way that when its thickness changed, the breakdown strength of the electric field changed over a wide range. Then, for the paper with the lowest average electric field intensity the possibility of explaining the complete breakdown by the breakdown of air segments on the basis of the Paschen dependence is checked. Further points of the obtained dependence by constructing models of papers of the same brand and a different thickness under the assumption of the similarity of electrostatic fields are determined. As such a criterion, the constancy of the equivalent effective permittivity are taken. Results. The dependence of the breakdown strength of the air in the range of 1.36...5.54 μm under normal conditions is determined. The obtained relationship is between the Peschot and Taev curves. Originality. For the first time, the possibility of indirectly estimation the breakdown strength of an insulating material using an electrostatic field model is indicated. Practical value. The proposed method for the numerical calculation of the breakdown voltage of air inclusions in the presence of water inclusions in the thickness of solid insulation can be applied to other types of solid thin-layer insulation., Полученная в работе зависимость напряженности электрического поля воздуха от длины разрядного промежутка удовлетворительно объясняет значения пробивных напряжений образцов конденсаторной бумаги при изменении их марок и толщины. Построена зависимость пробивной напряженности воздуха при нормальных условиях в диапазоне 1,36…5,54 мкм на основании расчета электростатических полей в моделях конденсаторной бумаги с сегментными поперечными сечениями цилиндрических объемов воздуха и воды. Проведено сопоставление полученной зависимости с известными экспериментальными данными. Полученные данные в диапазоне 2…5,54 мкм наиболее близки экспериментальным данным Пешо.
- Published
- 2020
10. A flow chemiluminescence paper-based microfluidic device for detection of chromium (III) in water
- Author
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Huijie Li, Chunsun Zhang, Rui Liu, Peng Zhang, and Qiuping Shang
- Subjects
Work (thermodynamics) ,Gravity (chemistry) ,Materials science ,Capillary action ,paper-based microfluidics ,Microfluidics ,Biomedical Engineering ,Medicine (miscellaneous) ,chemistry.chemical_element ,02 engineering and technology ,lcsh:Technology ,01 natural sciences ,law.invention ,Chromium ,law ,gravity flow ,lcsh:QC350-467 ,Chemiluminescence ,capillary flow ,lcsh:T ,010401 analytical chemistry ,detection of chromium (iii) ,Mechanics ,Paper based ,021001 nanoscience & nanotechnology ,chemiluminescence ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,Flow (mathematics) ,0210 nano-technology ,wax screen-printing ,lcsh:Optics. Light - Abstract
In this work, a solely gravity and capillary force-driven flow chemiluminescence (GCF-CL) paper-based microfluidic device has been proved for the first time as a new platform for inexpensive, usable, minimally-instrumented dynamic chemiluminescence (CL) detection of chromium (III) [Cr(III)], where an appropriate angle of inclination between the loading and detection zones on the paper produces a rapid flow of CL prompt solution through the paper channel. For this study, we use a cost-effective paper device that is manufactured by a simple wax screen-printing method, while the signal generated from the Cr(III)-catalyzed oxidation of luminol by H2O2 is recorded by a low-cost and luggable CCD camera. A series of GCF-CL affecting factors have been evaluated carefully. At optimal conditions, two linear relationships between GCF-CL intensities and the logarithms of Cr(III) concentrations are obtained in the concentration ranges of 0.025–35[Formula: see text]mg/L and 50–500[Formula: see text]mg/L separately, with the detection limit of 0.0245[Formula: see text]mg/L for a less than 30[Formula: see text]s assay, and relative standard deviations (RSDs) of 3.8%, 4.5% and 2.3% for 0.75, 5 and 50[Formula: see text]mg/L of Cr(III) ([Formula: see text]). The above results indicate that the GCF-CL paper-based microfluidic device possesses a receivable sensitivity, dynamic range, storage stability and reproducibility. Finally, the developed GCF-CL is utilized for Cr(III) detection in real water samples.
- Published
- 2019
11. Vibration analysis of paper machine’s asymmetric tube roll supported by spherical roller bearings
- Author
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Behnam Ghalamchi, Aki Mikkola, Janne Heikkinen, Jussi Sopanen, Jari Juhanko, Petri Kuosmanen, Raine Viitala, LUT University, Department of Mechanical Engineering, Aalto-yliopisto, and Aalto University
- Subjects
Timoshenko beam theory ,Materials science ,Spherical roller bearings ,Spherical roller bearing ,Aerospace Engineering ,02 engineering and technology ,01 natural sciences ,law.invention ,Physics::Fluid Dynamics ,Paper machine bearing defect ,0203 mechanical engineering ,law ,0103 physical sciences ,010301 acoustics ,Asymmetric rotor ,Civil and Structural Engineering ,Bearing (mechanical) ,ta214 ,Waviness ,Rotor (electric) ,Mechanical Engineering ,Mechanics ,Computer Science Applications ,Vibration ,Bearing waviness ,020303 mechanical engineering & transports ,Control and Systems Engineering ,Rolling-element bearing ,Signal Processing ,Subcritical vibrations ,Paper machine roll ,Beam (structure) - Abstract
This paper presents a simulation method that is used to study subcritical vibrations of a tube roll in a paper machine. This study employs asymmetric 3D beam elements based on the Timoshenko beam theory. An asymmetric beam model accounts for varying stiffness and mass distributions. Additionally, a detailed rolling element bearing model defines the excitations arising from the set of spherical roller bearings at both ends of the rotor. The results obtained from the simulation model are compared against the results from the measurements. The results indicate that the waviness of the bearing rolling surfaces contributes significantly to the subcritical vibrations while the asymmetric properties of the tube roll have only a fractional effect on the studied vibrations.
- Published
- 2018
12. Aging of oil-impregnated paper at different frequencies
- Author
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Weichuan Zhao and Mohamad Ghaffarian Niasar
- Subjects
Work (thermodynamics) ,Materials science ,Computer Science::Neural and Evolutionary Computation ,aging ,Oil-impregnated paper ,Mechanics ,Time–frequency analysis ,breakdown voltage ,high frequency electric stress ,Breakdown strength ,lifetime curve ,Waveform ,Breakdown voltage ,Peak value ,Voltage ,Weibull distribution - Abstract
In this work, breakdown strength and lifetime curve of oil-impregnated paper (OIP) are compared at 50Hz and 1500 Hz. For the ramp breakdown tests, sinusoidal voltage ramp of 1 kVp/s is used. The ramp breakdown experiments is conducted on OIP samples made of single and double sheets of OIP. Weibull plots and interpretation of the results are presented. In order to obtain lifetime curves, a step sinusoidal voltage waveform whose peak value is close to the minimum OIP ramp breakdown voltage is applied on single sheet of OIP samples. Time to breakdown is measured, and each experiment is repeated between 20-30 times to obtain good statistical results. The experiments were focused on four different voltage levels and the lifetime curves are plotted for those two target frequencies. Parameters of the lifetime curves are extracted and the interpretation is given.
- Published
- 2021
13. Axisymmetric acoustophoresis for paper pulp concentration
- Author
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Pierre Gelinas, Maxime Bilodeau, Romain Le Magueresse, Robert Schiavi, Tamara Krpic, and Nicolas Quaegebeur
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Materials science ,Acoustics and Ultrasonics ,QC221-246 ,02 engineering and technology ,engineering.material ,Acoustic levitation ,01 natural sciences ,Inorganic Chemistry ,Paper pulp concentration ,symbols.namesake ,stomatognathic system ,Pulp flow simulation ,Stokes' law ,Acoustophoresis ,Chemical Engineering (miscellaneous) ,Environmental Chemistry ,Radiology, Nuclear Medicine and imaging ,Original Research Article ,Acoustic radiation force ,QD1-999 ,Turbulence ,Pulp (paper) ,Papermaking ,010401 analytical chemistry ,Organic Chemistry ,Acoustics. Sound ,Mechanics ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Chemistry ,stomatognathic diseases ,Fiber suspension flow ,symbols ,engineering ,Particle ,Particle size ,0210 nano-technology - Abstract
Highlights • Numerical simulations of acoustophoresis in pulp flow is conducted. • Parametric study of fiber characteristics, pulp flow regimes and acoustic parameters are conducted. • A feasibility study of industrial acoustophoresis for pulp concentration is performed. • A potential concentration gain of 15% is obtained experimentally., In pulp and paper mills, mechanical processes such as screening and washing are commonly used to remove accumulated solid suspensions and concentrate the pulp. For environmental reasons and to optimize paper production, an emerging challenge is to develop alternative methods to concentrate paper pulp between 3 % and 6 % consistency for which the mixed pulp-water flow is complex. Among the proposed solutions in the literature, solutions based on acoustic levitation, also referred as acoustophoresis, of low-consistency pulp have been demonstrated as a potential solution for efficient pulp concentration and water recirculation. However, no sensitivity analysis on the ultrasound and physical parameters was proposed, limiting the extension to a realistic application. Thus, this paper presents a numerical modeling of acoustophoresis for pulp flow concentration in a pipe. For this purpose, the pulp flow is defined as a pseudo-homogenous fluid with a turbulent Low Re k- ∊ formalism, and the pulp particles are considered spherical and deflected by two acoustic forces, namely the acoustic radiation force and the Stokes drag force, both induced by an ultrasound wave generated along the walls of a circular pipe. The combined action of these two forces in the pulp flow enables to concentrate the particles at the center of the pipe. The influences of particle size and mechanical properties, fluid properties and ultrasound parameters are analyzed within a parametric study to optimize the particle deflection and the pulp concentration. The experimental feasibility of the industrial use of acoustophoresis for the concentration of paper pulp is demonstrated with a concentration gain up to 15 %.
- Published
- 2021
14. ROTATIONAL PAPER PULP VISCOMETER WITH MEASUREMENT AT TWO SHEAR SPEEDS
- Author
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O. V. Kril, O. M. Romaniuk, В. A. Kril, and H. B. Krykh
- Subjects
rotational viscometer ,Materials science ,Pulp (paper) ,Viscometer ,flow behavior index ,Mechanics ,Repeatability ,engineering.material ,paper pulp consistency measurement ,Power law ,Non-Newtonian fluid ,non-newtonian fluids ,effective viscosity ,consistency ratio ,Flow velocity ,engineering ,lcsh:SD1-669.5 ,General Earth and Planetary Sciences ,Torque ,lcsh:Forestry ,Friction torque ,General Environmental Science - Abstract
Maintaining of the proper predetermined paper pulp consistency on the different stages of the paper or cardboard manufacturing process significantly affects on quality and self cost of manufactured articles. The improvement of precision and repeatability of the paper pulp viscosity and consistency measurements is relevant to paper industry. Objective of the work is to improve the industrial-type paper pulp rotational consistometer. A new method for measurement of paper pulp concentration by means of a rotational viscometer was suggested which enables determining the flow consistency index K and flow behavior index n in the Ostwald-de Waele power law. The influence of the following torques on the measurement results is eliminated thanks to the new method: the friction torque in the seal of the sensitive element, the friction torque in the bearings of the shaft and the torque created under the influence of the flow with distorted flow speed profile. This is achieved by measuring the torque which acts on the sensitive element approaching the selected frequencies of sensitive element rotation both from the lower and higher frequencies. The mean torque value is calculated based on the obtained values. The measurements are conducted for two sensitive element rotation frequencies adjusted in advance. The frequency of sensitive element rotation is changed by means of a frequency converter. It is shown that by using two different rotation frequencies of the sensitive element of a rotational viscometer it is possible to define the flow consistency index and the flow behavior index. Paper pulp viscosity and consistency is defined on the basis of these two indexes. It is also suggested to average the results of viscous friction torque measurement approaching the rotation frequency of the viscometer sensitive element to the working frequency chosen for measurement from the lower and higher frequency ranges. By averaging the results of such measurement the friction torques in sealing and bearings supporting the sensitive element shaft are compensated. By changing the rotation direction of the sensitive element and by further averaging the obtained results it is possible to eliminate the influence of the asymmetrical distribution of paper pulp flow speed in the pipeline. This improves accuracy of the paper pulp consistency measurement.
- Published
- 2017
15. Wicking in Paper Strips under Consideration of Liquid Absorption Capacity
- Author
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Surasak Kasetsirikul, Nam-Trung Nguyen, and Muhammad J. A. Shiddiky
- Subjects
Materials science ,Capillary action ,paper-based microfluidics ,Flow (psychology) ,02 engineering and technology ,STRIPS ,absorption capacity ,01 natural sciences ,Capacitance ,Analytical Chemistry ,law.invention ,Physics::Fluid Dynamics ,lcsh:Biochemistry ,law ,wicking ,lcsh:QD415-436 ,Physical and Theoretical Chemistry ,Absorption (electromagnetic radiation) ,Electronic circuit ,ComputingMethodologies_COMPUTERGRAPHICS ,010401 analytical chemistry ,Mechanics ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Electrical network ,electrical circuit analogy ,Current (fluid) ,0210 nano-technology - Abstract
Paper-based microfluidic devices have the potential of being a low-cost platform for diagnostic devices. Electrical circuit analogy (ECA) model has been used to model the wicking process in paper-based microfluidic devices. However, material characteristics such as absorption capacity cannot be included in the previous ECA models. This paper proposes a new model to describe the wicking process with liquid absorption in a paper strip. We observed that the fluid continues to flow in a paper strip, even after the fluid reservoir has been removed. This phenomenon is caused by the ability of the paper to store liquid in its matrix. The model presented in this paper is derived from the analogy to the current response of an electric circuit with a capacitance. All coefficients in the model are fitted with data of capillary rise experiments and compared with direct measurement of the absorption capacity. The theoretical data of the model agrees well with experimental data and the conventional Washburn model. Considering liquid absorption capacity as a capacitance helps to explain the relationship between material characteristics and the wicking mechanism.
- Published
- 2020
16. Description of space charge transport in oil‐paper insulation using adaptive time‐stepping transient upstream finite element method
- Author
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Jiefeng Liu, Yiyi Zhang, Wei Zhang, Bing Gao, Mingchen Shi, and Shuo Liang
- Subjects
QC501-721 ,Materials science ,Electricity ,Time stepping ,Energy Engineering and Power Technology ,Upstream (networking) ,Electrical engineering. Electronics. Nuclear engineering ,Mechanics ,Transient (oscillation) ,Electrical and Electronic Engineering ,Space charge ,Finite element method ,TK1-9971 - Abstract
The charge transport and accumulation in oil–paper can cause the insulation degradation. So far, the most widely used model to simulate space charge transport and accumulation is the bipolar charge transport (BCT) model, which can well simulate the space charge dynamics. However, there are two shortcomings in the algorithms for solving the BCT model. One is that there is almost no use of vectorisation technology, which may increase the complexity of the algorithm, the other is the usage of fixed step size which might bring extra computation cost. In view of this, an adaptive time‐stepping transient upstream finite element method (FEM) is developed to solve the BCT model considering trapping/detrapping, as well as the recombination phenomenon under DC condition in this article. Then, a vectorisation technology is used in the method to optimise the algorithm. Moreover, the adaptive time‐stepping method is introduced in simulation to reduce computation time and calculation amount. Simulation results are obtained by programing and later presented, which are basically consistent with the corresponding experimental results. Therefore, the proposed method is expected to promote the optimization design of the oil–paper insulation system.
- Published
- 2021
17. The Mechanics of Intervention and the Green Paper on Land Reform
- Author
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Juanita Pienaar
- Subjects
Government ,Sociology and Political Science ,National Development Plan ,Green paper ,Land law ,Legislation ,Mechanics ,Public administration ,Collective impact ,Intervention (law) ,Law ,Sociology ,Land reform - Abstract
The South African land control system has always, to some extent, been interfered with by government. Interventions in the course of the twentieth century in particular have resulted in an unequal, fragmented and diverse land control system. The law has been integral to this process. Since 1994, within a constitutional paradigm, interventions have been aimed at untangling the complex web of land-related measures so as to affect an equitable, co-ordinated and less complex land system. In this process law - including policy documents, plans, programmes and legislative measures - is again integral. The aim of this contribution is to ascertain whether, under the present government, the mechanics of intervention within the land reform arena have resulted overall in a sensible, workable framework within which challenges and weaknesses linked to land reform can be addressed effectively. In this regard both the structural and material dimensions of recent interventions are set out. Within this context the most recent intervention dealing with land reform in particular, the Green Paper on Land Reform of 2011, is placed in perspective and investigated further in light of the recent National Development Plan. Specific themes that have resonated in the recent mechanics of intervention, as well as the persons and communities who stand to be affected by them and the possible extent of their collective impact, are thereafter discussed. Due to the general vagueness of the Green Paper and its lack of depth and detail, the extent of the impact of the recent measures cannot be ascertained fully. The alignment of the new bodies and institutions proposed by and their contribution to actually addressing the challenges identified in the Green Paper are furthermore problematic and disappointing. Excluding vast portions of rural land comprising communal areas from all of the recent tenure-related measures is especially disconcerting. Clearly, huge gaps prevail in the resultant framework. Overall, the analysis of the recent structural and material dimensions of the recent mechanics underlines that further engineering is urgently required.
- Published
- 2017
18. Nonlinear Dielectric Response Characteristics of Damp Oil-Paper Insulation and Application of H-W Model in Time-Frequency Conversion
- Author
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Lijun Yang, Zhen Qin, Wei Li, Xingjun Guo, Yingxin Deng, Wei Nie, and Ruijin Liao
- Subjects
010302 applied physics ,Work (thermodynamics) ,Materials science ,Mechanics ,01 natural sciences ,Domain (software engineering) ,Time–frequency analysis ,symbols.namesake ,Nonlinear system ,Fourier transform ,Frequency domain ,0103 physical sciences ,symbols ,Time domain ,Electrical and Electronic Engineering ,Debye model - Abstract
In this work, the extended Debye model or Fourier transform is adopted to convert the polarization and depolarization current test results from the time domain into the frequency domain at low frequencies, thereby shortening the test time but producing large errors when the oil-paper insulation exhibits nonlinear characteristics. The voltage-current response characteristics of samples with three different moisture contents are tested to study the influence of moisture on the nonlinear characteristics. Hammerstein-Wiener (H-W) equivalent mathematical model is proposed for time-frequency domain conversion, and the results from this model and two formal methods are compared. The findings show that the errors of the two conventional methods increase with nonlinearity. The H-W model accurately depicts the nonlinear dielectric response of oil-paper insulation and thus can provide high-precision time-frequency domain conversion data.
- Published
- 2020
19. Calibration of filter paper for measuring total soil suction
- Author
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S. P. Bajad, S. R. Khandeshwar, S. P. Raut, and P. B. Pande
- Subjects
Suction ,Filter paper ,Calibration curve ,Calibration (statistics) ,General Chemical Engineering ,General Engineering ,General Physics and Astronomy ,Mechanics ,Exponential function ,General Earth and Planetary Sciences ,General Materials Science ,Relative humidity ,Osmotic coefficient ,General Environmental Science ,Mathematics - Abstract
Calibration curve plays an important role in filter paper method because it affects accuracy in soil suction values. Osmotic coefficient and relative humidity govern the osmotic suction required to develop calibration curve and equation. Most of the researchers used the readily available total (osmotic) suction values from various studies to develop the calibration curve. Very few researchers used the osmotic coefficient in calibration and studied its effect on calibration and measuring suction. In this paper, the effect of the osmotic suction proposed by various researchers on calibration of Whatman 42 Filter paper was studied. Logarithmic and exponential calibration equations were developed and compared. The NaCl solution used in the present study provides limited total suction range of 0–30,000 kPa. The total suction of clayey soil was measured to validate the calibration curves proposed in this study. The feasibility of proposed osmotic coefficients is verified by measuring total suction of soil. The total suction estimated from calibration curve using osmotic coefficients was found to be more accurate.
- Published
- 2019
20. The Influence of Pressure on the Discharge along Oil-Paper Interface under AC Stress
- Author
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Liu Kai, Bo Gao, Zhou Peng, Yan Yang, Yu Rui, Guangning Wu, and Guangcai Hu
- Subjects
Control and Optimization ,Materials science ,white mark ,Bubble ,flashover ,Hydrostatic pressure ,Energy Engineering and Power Technology ,01 natural sciences ,lcsh:Technology ,oil-paper interface ,010305 fluids & plasmas ,law.invention ,Stress (mechanics) ,law ,0103 physical sciences ,Arc flash ,bubble effect ,Electrical and Electronic Engineering ,Engineering (miscellaneous) ,normal operating condition ,010302 applied physics ,Renewable Energy, Sustainability and the Environment ,lcsh:T ,Mechanics ,Dissipation ,partial discharge ,Partial discharge ,hydrostatic pressure ,Hydrostatic equilibrium ,Energy (miscellaneous) ,Voltage - Abstract
This study explores the influence of hydrostatic pressure on the discharge along the oil-paper interface under AC voltage, especially for the normal operating condition and breakdown. In this paper, an experimental platform was set up to record the partial discharge (PD) parameters of the test sample under different hydrostatic pressures, while the applied AC voltage was increased to final flashover voltage step by step. Experimental results showed that higher hydrostatic pressure had different effects on PD under different voltages. Higher pressure decreased the PD energy and increased the flashover voltage. Furthermore, under higher hydrostatic pressure, discharge traces (white mark) were found on the surface of the samples after intense discharging on the oil-paper interfaces, indicating that the hydrostatic pressure can affect the gas generation and dissipation process underneath the surface of the pressboards. Finally, the mechanism of how hydrostatic pressure influences the PD, flashover voltage, and white mark was interpreted based on the bubble theory. The results derived in this paper can be helpful for an optimal design and reasonable operation of oil-paper insulation systems, especially for power transformers.
- Published
- 2019
21. Charging and Discharging Current Measurements and Impact of Polarization Dynamics on Electric Field Modeling in HVDC Paper-Insulated Cables
- Author
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Pasquale Cambareri, Carlo De Falco, Luca Di Rienzo, Paolo Seri, Gian Carlo Montanari, Cambareri P., De Falco C., Di Rienzo L., Seri P., and Montanari G.C.
- Subjects
Permittivity ,Electric fields ,Materials science ,General Computer Science ,Field (physics) ,020209 energy ,02 engineering and technology ,Dielectric ,HVDC transmission ,01 natural sciences ,Electric fields, Transient analysis, Current measurement, HVDC transmission, Permittivity, Mathematical model, Dielectrics ,Transient analysis ,Mathematical model ,electric field transient ,dielectric polarization ,Insulation system ,Electric field ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,Polarization (electrochemistry) ,010302 applied physics ,General Engineering ,Mechanics ,Current measurement ,HVDC cables ,Dielectrics ,electrical insulation ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,Transient (oscillation) ,lcsh:TK1-9971 ,Voltage - Abstract
Accurate modeling and simulation of electric field transients in HVDC cables is an important support to optimize insulation system design and to evaluate the influence of voltage transients and steady-state conditions on accelerated ageing mechanisms and insulation reliability. Traditionally, field models considering time-independent permittivity and conductivity are used, but this approach neglects polarization mechanisms and charge trapping-detrapping phenomena. This article includes polarization dynamics in the field model and shows that its impact on transient electric field simulations in HVDC paper-insulated cables can be significant. A method is presented to infer the model parameters from experimental polarization and depolarization current measurements.
- Published
- 2021
22. Application of Paper Folding Technique to Three-Dimensional Space Sound Absorber with Permeable Membrane: Case Studies of Trial Productions
- Author
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Kimihiro Sakagami, Hirotaka Suzuki, Masahiro Toyoda, Takeshi Okuzono, and Nao Koyanagi
- Subjects
Materials science ,Semipermeable membrane ,Mechanics ,Folding (DSP implementation) ,Sound Absorber ,Three-dimensional space - Abstract
The authors propose a space sound absorber made of a permeable membrane (PM), including woven or non-woven fabrics in three-dimensional shapes, e.g., cylinder, rectangle, etc. The proposed absorbers are examined by experimental measurements and boundary element analyses, and it is found that they can be effectively used especially for middle and high frequencies. In order to develop these absorbers for wider applications, it would be desirable to give them additional values and functions, particularly to elaborate on their design. Supposing that they could also be used for lighting equipment, such as lampshades as one of the applications, pilot studies on pseudo-cylindrical, and pseudo-spherical PM space absorbers with uneven surfaces produced by paper-folding (origami technique) are carried out. The pseudo-cylindrical concave curves (PCCC) shell shape has been proven as a suitable form for a lampshade, and the pseudo-spherical concave curves (PSCC) shell shape is an application of PCCC. In this paper, PCCC and PSCC shell shapes are applied to three-dimensional PM space absorbers, and trials are conducted using PMs selected by flow resistance measurements and preliminary simulations. The sound absorptivity of the specimens is measured in a reverberation chamber, and their absorptivity is 0.6 (PCCC case) and 0.4 (PSCC case) at mid-high frequencies.
- Published
- 2020
23. Breakdown and streamer behavior in double-layer oil-paper insulation under impulses of varying front time
- Author
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Qiaogen Zhang, Heli Ni, Chong Guo, and Tao Wen
- Subjects
010302 applied physics ,Imagination ,Materials science ,Impulse testing ,Dielectric strength ,Physics::Instrumentation and Detectors ,media_common.quotation_subject ,Mechanics ,Impulse (physics) ,01 natural sciences ,Space charge ,Voltage amplitude ,Physics::Plasma Physics ,0103 physical sciences ,Breakdown voltage ,Electrical and Electronic Engineering ,media_common ,Voltage - Abstract
The breakdown and streamer behavior in double-layer oil-paper insulation under impulses of varying front time were investigated in this study to determine the prebreakdown process in oil-paper insulation. The relationships between front times and breakdown characteristics were investigated and impulse-polarity-dependent variations were observed. The complete impulse breakdown process and precise role of front time were assessed as per streamer initiation and streamer propagation based on emitted light signals and shadow images. The re-initiation of streamers in non-first oil gaps was determined to be the key factor in breakdown as-dominated by applied voltage and space charge accumulation. The initiation and propagation times of streamers were observed to find that the streamers tend to propagate at phases with higher voltage amplitude as front time increases, which facilitates streamer re-initiation and thus decreases the breakdown voltage. Equivalent applied voltages during streamer propagation were further calculated to quantitatively investigate the effect of front time on streamer propagation.
- Published
- 2020
24. FLUID FLOW BODIES FOR THE PULP AND PAPER INDUSTRY
- Author
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Yuriy Davidovich Alashkevich, Ol'ga Mikhaylovna Lur’e, Mikhail Semenovich Lur’e, and Aleksandr Sergeyevich Frolov
- Subjects
Physics ,010405 organic chemistry ,Organic Chemistry ,Flow (psychology) ,Plant Science ,Mechanics ,Vortex generator ,01 natural sciences ,Noise (electronics) ,0104 chemical sciences ,Working range ,Volumetric flow rate ,Biomaterials ,010404 medicinal & biomolecular chemistry ,symbols.namesake ,Flow velocity ,symbols ,Strouhal number ,Suspension (vehicle) - Abstract
The question of the use of vortex flowmeters with different versions of the flow body (TO) under operating conditions on the technological lines of pulp and paper production is considered. It is shown that when using different TO in vortex flowmeters, an error occurs in the working range of speeds (flow rates). The observed error arises due to a change in the Strouhal number (Sh) and is associated with the measurement method. In this case, the Strouhal number begins to depend not only on the TO used as a vortex generator, but also on the flow velocity and the concentration of the fibrous suspension. As the main comparative factor for the investigated TOs, the force action on the sensitive element (flexible electrode) located inside the TO was taken. The study was carried out in several stages using numerical modeling and experimental design method. According to the results of a numerical study, the dependence of the Strouhal number (Sh) on the flow rate (V) and the concentration of the suspension (c) is presented. In a comparative analysis of the deviation of the Strouhal number from the average values, it was revealed that MOT No. 1 has a minimal effect on the concentration of the suspension in the working range of flow rates (± 0.5%). This circumstance makes it possible to verify and test flow meters with such maintenance in conventional pouring installations. The analysis of the maintenance with respect to the signal-to-noise ratio shows that the purest signal is generated by the cylindrical maintenance (maintenance No. 3), and maintenance No. 2 and No. 1 have noticeably large noise. The differences are explained by the absence on the surface of a cylindrical TO of extra protrusions, faces, which leads to a smoother flow of a suspension around its surface, as well as to a decrease in internal spurious noise.
- Published
- 2020
25. Radial Imbibition in Paper under Temperature Differences
- Author
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J. M. Gomba, F. J. Higuera, Jonatan Raúl Mac Intyre, Abraham Medina, Carlos Alberto Perazzo, and Abel López-Villa
- Subjects
Materials science ,Ciencias Físicas ,THERMOCAPILLARY PHENOMENA ,02 engineering and technology ,lcsh:Thermodynamics ,7. Clean energy ,01 natural sciences ,IMBIBITION ,Darcy–Weisbach equation ,010305 fluids & plasmas ,Aeronáutica ,Surface tension ,purl.org/becyt/ford/1 [https] ,thermocapillary phenomena ,porous media ,020401 chemical engineering ,lcsh:QC310.15-319 ,0103 physical sciences ,imbibition ,0204 chemical engineering ,Blotting paper ,Porosity ,lcsh:QC120-168.85 ,Fluid Flow and Transfer Processes ,Física de los Fluidos y Plasma ,Mechanical Engineering ,POROUS MEDIA ,Single parameter ,Mechanics ,purl.org/becyt/ford/1.3 [https] ,Condensed Matter Physics ,lcsh:Descriptive and experimental mechanics ,Imbibition ,Porous medium ,CIENCIAS NATURALES Y EXACTAS - Abstract
Spontaneous radial imbibition into thin circular samples of porous material when they have been subjected to radial temperature differences was analyzed theoretically and experimentally. The use of the Darcy equation allows us to take into account temperature variations in the dynamic viscosity and surface tension in order to found the one-dimensional equation for the imbibition fronts. Experiments in blotting paper show the good fit between the experimental data to theoretical profiles. Fil: Lopez Villa, Abel. Instituto Politécnico Nacional. Centro de Investigación y de Estudios Avanzados. Departamento de Investigaciones Educativas.; México Fil: Medina, Abraham. Instituto Politécnico Nacional. Centro de Investigación y de Estudios Avanzados. Departamento de Investigaciones Educativas.; México Fil: Higuera, F. J.. No especifíca; Fil: Mac Intyre, Jonatan Raúl. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física Arroyo Seco; Argentina Fil: Perazzo, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Medicina Traslacional, Trasplante y Bioingeniería. Fundación Favaloro. Instituto de Medicina Traslacional, Trasplante y Bioingeniería; Argentina Fil: Gomba, Juan Manuel. Universidad Favaloro; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Tandil. Centro de Investigaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires. Sede Olavarria del Centro de Investifaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires | Universidad Nacional del Centro de la Pcia.de Bs.as.. Centro de Investigaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires. Sede Olavarria del Centro de Investifaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires.; Argentina
- Published
- 2019
- Full Text
- View/download PDF
26. Liquid film thickness of two‐phase slug flows in capillary microchannels: A review paper
- Author
-
Yuri S. Muzychka, Amin Etminan, and Kevin Pope
- Subjects
Liquid film ,Microchannel ,Materials science ,biology ,Capillary action ,Slug ,General Chemical Engineering ,Phase (matter) ,Two-phase flow ,Mechanics ,Slug flow ,biology.organism_classification - Published
- 2021
27. Heat and Mass Transfer on Free Path Portions in Drying Paper in Multicylinder Contact-Convective Units
- Author
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A. G. Nikolaeva, V. Yu. Lakomkin, and E. N. Gromova
- Subjects
Convection ,Imagination ,Chemical substance ,Materials science ,Convective heat transfer ,media_common.quotation_subject ,General Engineering ,Mechanics ,Condensed Matter Physics ,Physics::Fluid Dynamics ,Mass transfer ,Path (graph theory) ,Water content ,Physics::Atmospheric and Oceanic Physics ,media_common - Abstract
Convective heat- and mass-transfer processes are considered that occur on free surfaces of a wet paper web in an air medium with a single-row arrangement of drying cylinders. Calculated dependences are determined making it possible to predict the duration of the process of drying the paper web in multicylinder contact-convective units.
- Published
- 2019
28. Analysis of representative elementary volume and through-plane regional characteristics of carbon-fiber papers: diffusivity, permeability and electrical/thermal conductivity
- Author
-
Jeff T. Gostick, Marcos Vera, Pablo A. García-Salaberri, Iryna V. Zenyuk, Gisuk Hwang, Adam Z. Weber, Andrew Shum, and Ministerio de Economía y Competitividad (España)
- Subjects
Length scale ,Materials science ,020209 energy ,Lattice Boltzmann methods ,Mass diffusivity ,02 engineering and technology ,Thermal diffusivity ,Carbon-fiber paper ,Ingeniería Industrial ,Energy conversion and storage ,Thermal conductivity ,0202 electrical engineering, electronic engineering, information engineering ,Effective properties ,Fluid Flow and Transfer Processes ,Ingeniería Mecánica ,Mechanical Engineering ,Modeling ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Durability ,Representative elementary volume ,Tomography ,0210 nano-technology ,X-ray tomography - Abstract
Understanding the transport processes that occur in carbon-fiber papers (CFPs) used in fuel cells, electrolyzers, and metal-air/redox flow batteries is necessary to help predict cell performance and durability, optimize materials and diagnose problems. The most common technique used to model these thin, heterogeneous, anisotropic porous media is the volume-averaged approximation based on the existence of a representative elementary volume (REV). However, the applicability of the continuum hypothesis to these materials has been questioned many times, and the error incurred in the predictions is yet to be quantified. In this work, the existence of a REV in CFPs is assessed in terms of dry effective transport properties: mass diffusivity, permeability and electrical/thermal conductivity. Multiple sub-samples with different widths and thicknesses are examined by combining the lattice Boltzmann method with X-ray tomography images of four uncompressed CFPs. The results show that a meaningful length scale can be defined in the material plane in the order of 1–2 mm, which is comparable to the rib/channel width used in the aforementioned devices. As for the through-plane direction, no distinctive length scale smaller than the thickness can be identified due to the lack of a well-defined separation between pore and volume-averaged scales in these inherently thin heterogeneous materials. The results also show that the highly porous surface region (amounting up to 20% of the thickness) significantly reduces the through-plane electrical/thermal conductivity. Overall, good agreement is found with previous experimental data of virtually uncompressed CFPs when approximately the full thickness is considered. The authors thank the support team of Calcul Quebec and Compute Canada for their help during the simulation campaign, as well as Dr. Dula Parkinson and Dr. Alastair MacDowell at the Advanced Light Source (ALS) for help in obtaining the tomographic images. This work was funded under the Fuel Cell Performance and Durability Consortium (FC-PAD), by the Fuel Cell Technologies Office (FCTO), Office of Energy Efficiency and Renewable Energy (EERE), of the U.S. Department of Energy under contract number DE-AC02-05CH11231, Project ENE2015-68703-C2-1-R (MINECO/FEDER, UE) and the research grant 'Ayudas a la Investigation en Energia y Medio Ambiente' awarded to the first author by the Spanish lberdrola Foundation. I.V. Zenyuk and A.D. Shum would like to acknowledge support from the National Science Foundation under CBET Award 1605159. X-ray tomography experiments were performed on beamline 8.3.2 at the ALS (Lawrence Berkeley National Laboratory), which is a national user facility funded by the Department of Energy, Office of Basic Energy Sciences under contract DE-ACO2-05CH11231. Numerical calculations were performed on the supercomputing clusters Briaree, Colosse, Guillimin and Mp2, managed by Calcul Quebec and Compute Canada. The operation of these supercomputers is funded by the Canada Foundation for Innovation (CFI), Ministere de l'Economie, de l'Innovation et des Exportations du Quebec (MEIE), RMGA and the Fonds de recherche du Quebec -Nature et technologies (FRQ-NT).
- Published
- 2018
29. Comment on the paper 'MHD slip flow of a dissipative Casson fluid over a moving geometry with heat source/sink: A numerical study, C.S.K. Raju, N. Sandeep, Acta Astronautica 133 (2017) 436–443'
- Author
-
Asterios Pantokratoras
- Subjects
Source sink ,Physics ,Slip flow ,Dissipative system ,Aerospace Engineering ,Casson fluid ,Mechanics ,Magnetohydrodynamics - Published
- 2021
30. [Paper] Droplet Formulation Method for Viscous Fluid Injection Considering the Effect of Liquid-Liquid Two-Phase Flow
- Author
-
Nobuhiko Mukai, Masamichi Oishi, Takuya Natsume, and Marie Oshima
- Subjects
Surface tension ,Fluid simulation ,Computer science ,Signal Processing ,Media Technology ,Particle method ,Liquid liquid ,Two-phase flow ,Mechanics ,Viscous liquid ,Computer Graphics and Computer-Aided Design - Published
- 2021
31. Correction to 'Experimental Measurement of Parameters Governing Flow Rates and Partial Saturation in Paper-Based Microfluidic Devices'
- Author
-
Bhushan J. Toley, N. Sathishkumar, and Dharitri Rath
- Subjects
Materials science ,Partial saturation ,Microfluidics ,Electrochemistry ,General Materials Science ,Surfaces and Interfaces ,Paper based ,Mechanics ,Condensed Matter Physics ,Spectroscopy ,Volumetric flow rate - Published
- 2019
32. Mechanism and numerical model of bubble effect in oil-paper insulation based on microtubule model
- Author
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Chenhao Jia, Tao Zhao, Yixin Tong, Liu Yunpeng, and Nijie Chao
- Subjects
010302 applied physics ,Pressboard ,Materials science ,Bubble ,Mechanics ,Microstructure ,01 natural sciences ,Ideal gas ,law.invention ,Physics::Fluid Dynamics ,law ,0103 physical sciences ,Growth rate ,Electrical and Electronic Engineering ,Transformer ,Porosity ,Physical quantity - Abstract
In this paper, a numerical model of bubble evolution is established by studying the microstructure of pressboard and the physical process of bubble generation. In the model, the porous structure of fibers is equivalent to microtubules, the gases in the bubbles are classified into two categories, and the ideal gas state equation is used to describe the bubble state. Then the pressure conditions at the bubble boundary and the evaporation rate of water are taken as solution conditions to solve the physical quantities in the state equation. The numerical model provides a new way to calculate the initial temperature of bubble escape (ITBE). And the bubble evolution inside the pressboard is obtained which is hard to be observed in experiment. After that, the influences of moisture content of pressboard and cellulose aging on ITBE in the numerical model are discussed. The model results show that the expansion rate of bubble is not uniform. Bubble growth is slow in the early stage of temperature rise, when the temperature reaches a certain threshold the growth rate of bubble radius increases significantly, which is of great significance to the temperature limit on oil-immersed power transformers.
- Published
- 2020
33. Partial Discharge Simulation of Air Gap Defects in Oil-Paper Insulation Paperboard of Converter Transformer under Different Ratios of AC–DC Combined Voltage
- Author
-
Licheng Li, Jia Lei, Tingting Wang, Dong Dai, Luo Bing, and Jian Wang
- Subjects
Technology ,Pressboard ,Control and Optimization ,Materials science ,surface charge density ,Renewable Energy, Sustainability and the Environment ,partial discharge ,combined voltage ,space charge ,Energy Engineering and Power Technology ,Mechanics ,Space charge ,law.invention ,law ,Partial discharge ,Electrical and Electronic Engineering ,Transformer ,Air gap (plumbing) ,Engineering (miscellaneous) ,Polarity (mutual inductance) ,Energy (miscellaneous) ,Voltage ,DC bias - Abstract
A converter transformer is important primary equipment in a DC transmission project. The voltage on the valve side winding is complex when the equipment is running, including DC, AC, and AC–DC combined voltage. The insulation structure of the valve side winding of a converter transformer is an oil-paper insulation structure, which may have a variety of defects in the manufacturing stage and daily use, resulting in partial discharge. Therefore, it is the key to studying the partial discharge characteristics and mechanism of oil-paper insulation under AC–DC combined voltage. In this paper, we build a two-dimensional air gap model of oil-paper-insulated pressboard considering the actual particles and actual reaction based on the fluid model. The characteristics and evolution mechanism of partial discharge (PD) in pressboard under different AC/DC combined voltages are studied by numerical simulation. The results show that when the DC component increases, the polarity effect of partial discharge is more obvious, while the potential and discharge intensity in the air gap decrease. Further analysis revealed that the DC component in the combined voltage accumulated a large number of surface charges on the surface of the air gap, and the space charge distribution was more uniform and dispersed, which generated an electric field with opposite polarity to the DC component in the air gap and, then, inhibited the development of local discharge in the paperboard. The results of the simulation are consistent with the previous experimental phenomena, and the mechanism analysis of the simulation results also verifies the previous analysis on the mechanism of experimental phenomena. This will lay a theoretical foundation for the further study of partial discharge phenomenon of oil-paper insulation structures in practical operation in the future.
- Published
- 2021
- Full Text
- View/download PDF
34. Design and simulation of fluid flow in paper based microfluidic platforms
- Author
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Aarathi Pradeep, Nidhin T. Madhu, T.G. Satheesh Babu, and P.E. Resmi
- Subjects
Work (thermodynamics) ,Materials science ,Filter paper ,Multiphysics ,Reagent ,Microfluidics ,Fluid dynamics ,Mechanics ,Thermal diffusivity ,Porous medium - Abstract
Computational simulation for the fluid flow in a paper based microfluidic system was performed and was experimentally validated in this work. Comsol Multiphysics based simulation was performed and the module used was species transport in porous medium. Two separate simulation for the reagent distribution and the interaction of sample with the immobilized reagent in paper based microfluidics devices were carried out. This was performed by varying the parameters such as adsorption constant, diffusivity and average velocity of fluid in the porous medium for finding the concentration profile. Finer mesh were used for the simulation which gives more accurate results with less computational time. The reagent distribution was experimentally validated by dropping methylorange indicator over Whatman filter paper.
- Published
- 2019
35. New Method for Shallow and Deep Trap Distribution Analysis in Oil Impregnated Insulation Paper Based on the Space Charge Detrapping
- Author
-
Jian Hao, Runhao Zou, Ruijin Liao, Li-Jun Yang, and Qiang Liao
- Subjects
Control and Optimization ,Materials science ,electrical field ,020209 energy ,Energy Engineering and Power Technology ,02 engineering and technology ,Trapping ,01 natural sciences ,lcsh:Technology ,Trap (computing) ,Electric field ,0103 physical sciences ,oil ageing ,0202 electrical engineering, electronic engineering, information engineering ,Physics::Atomic Physics ,Electrical and Electronic Engineering ,Engineering (miscellaneous) ,trap distribution ,oil impregnated insulation paper ,010302 applied physics ,Condensed Matter::Quantum Gases ,Range (particle radiation) ,Renewable Energy, Sustainability and the Environment ,lcsh:T ,Double exponential function ,Mechanics ,Space charge ,Exponential function ,Distribution (mathematics) ,charge detrapping ,space charge ,Energy (miscellaneous) - Abstract
Space charge has close relation with the trap distribution in the insulation material. The phenomenon of charges trapping and detrapping has attracted significant attention in recent years. Space charge and trap parameters are effective parameters for assessing the ageing condition of the insulation material qualitatively. In this paper, a new method for calculating trap distribution based on the double exponential fitting analysis of charge decay process and its application on characterizing the trap distribution of oil impregnated insulation paper was investigated. When compared with the common first order exponential fitting analysis method, the improved dual-level trap method could obtain the energy level range and density of both shallow traps and deep traps, simultaneously. Space charge decay process analysis of the insulation paper immersed with new oil and aged oil shows that the improved trap distribution calculation method can distinguish the physical defects and chemical defects. The trap density shows an increasing trend with the oil ageing, especially for the deep traps mainly related to chemical defects. The greater the energy could be filled by the traps, the larger amount of charges could be trapped, especially under higher electric field strength. The deep trap energy level and trap density could be used to characterize ageing. When one evaluates the ageing condition of oil-paper insulation using trap distribution parameters, the influence of oil performance should not be ignored.
- Published
- 2018
36. Energy and paper recycling: Modelling the time and energy requirements for low consistency batch repulping
- Author
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James A. Olson, Frank Saville, and Mark Martinez
- Subjects
0106 biological sciences ,Engineering ,Engineering drawing ,business.industry ,Turbulence ,General Chemical Engineering ,Baffle ,02 engineering and technology ,Mechanics ,Power number ,Dissipation ,021001 nanoscience & nanotechnology ,01 natural sciences ,Paper recycling ,Surface-area-to-volume ratio ,010608 biotechnology ,0210 nano-technology ,business ,Material properties ,Complete mixing - Abstract
An analytical model for low-consistency repulping linking pulp material properties, consistency, temperature, and rotor and vat geometry is provided, which allows for accurate prediction of the time and energy required for repulping in both a 0.25 m3 laboratory-scale repulper and a 15 m3 industrial-scale repulper. The model assumes that all deflaking work is done by the repulper rotor in the rotor-swept volume by turbulence generated by the rotor and that no deflaking occurs in the rest of the vat. Rotor shaft power is split linearly between the breakup of waste paper and dissipation by turbulence. Comparing the model predictions and experimental data for different pulp types, vat fill levels, and pulp suspension consistencies yields a correlation of R2 = 0.99 between all experimental results and the model predictions given the condition of fully turbulent (Reynolds-independent) repulper rotor operation. The efficiency of the laboratory repulper is reduced from that predicted by the model for very low vat fill levels. This is due to a loss of effectiveness of the baffles at these low levels as indicated by solid body motion of the suspension and reduced rotor power number. This indicates that thorough mixing is a requirement to maximize repulping efficiency. Repulping time and energy savings can be accomplished by increasing the suspension consistency and the rotor-swept volume/vat volume ratio by either increasing rotor size or reducing vat volume, all while ensuring complete mixing and circulation in the vat.
- Published
- 2016
37. Studying droplet adhesion to fibers using the magnetic field: a review paper
- Author
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Hooman Vahedi Tafreshi and M. Jamali
- Subjects
Fluid Flow and Transfer Processes ,Coalescence (physics) ,endocrine system ,Materials science ,technology, industry, and agriculture ,Computational Mechanics ,General Physics and Astronomy ,Context (language use) ,Adhesion ,Mechanics ,engineering.material ,complex mixtures ,eye diseases ,law.invention ,Magnetic field ,Physics::Fluid Dynamics ,Coating ,Mechanics of Materials ,law ,Physics::Atomic and Molecular Clusters ,engineering ,Liquid flow ,A fibers ,Filtration - Abstract
This paper presents a brief overview of the use of magnetic field in studying droplet adhesion to a fiber or a fibrous surface. The paper starts by discussing ways to quantify the force required to detach a droplet from a fiber for its applications in coalescence filtration, i.e., removal of dispersed droplets from a gaseous or liquid flow using a fibrous filter. It then continues to discuss droplet detachment from a fibrous surface or penetrating into a thin fibrous coating. The emphasis is put on a recently develop magnetic approach for measuring force of detachment and on its novel simplicity and non-intrusive nature in the context of existing droplet detachment methods. Our review also includes a discussion on force of detachment for multiphase droplets comprised of two immiscible liquids, i.e., compound droplets. Atomistic- and continuum-level numerical simulations pertaining to droplet detachment are also discussed throughout the paper when appropriate.
- Published
- 2021
38. Interface charge behavior of multi-layer oil–paper insulation under DC and polarity reversal voltages
- Author
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Boxue Du, Jinrui Zhang, and Daosheng Liu
- Subjects
Polarity reversal ,Engineering ,Transformer oil ,business.industry ,Electrical insulation paper ,Electrical engineering ,Mechanics ,Space charge ,law.invention ,law ,Insulation system ,High-voltage direct current ,Electrical and Electronic Engineering ,Transformer ,business ,Voltage - Abstract
Transformer oil, insulating paper, high voltage direct current (HVDC) bushings and on-load tap changer (OLTC) are essential parts of converter transformers. When the power flow of the HVDC system is reversed or a sudden outrage occurs, the charge field will deform the dielectric internal electric field, thus easily leading to the occurrence of discharge or insulation damage. In this case, it is necessary to carry out the characterization of the oil–paper interface to avoid these consequences. This paper analyses the interface charge accumulation and dissipation characteristics of an oil–paper insulation system under DC and polarity reversal voltages. In this paper, induced electrification was used to charge the composite oil–paper insulation. The amplitude of DC and polarity reversal voltages applied in this paper was 4 kV, and paper with thicknesses of 0.08 and 0.13 mm was used. This research offers a theoretical exploration to optimize the transformer oil– paper insulation structure and prevent damage to its insulation systems. From the research on different layers and thicknesses of paper, it can be concluded that the decay is fast in the initial period and then becomes slower with the lapse of time until finally the decay curve tends to become flat. With an increase in the number of the paper layers, the interface charge density decreases. So in real life multilayer paper is used to avoid failures owing to its structural weakness. Regarding the DC polarity reversal effect, increasing the thickness of the paper is equivalent to adding paper layers. The dissipation rate of the positive interface charge is quicker than that of the negative one. In the polarity reversal test, the dissipation rate becomes smaller as the reversal time gets longer.
- Published
- 2015
39. Preface to special issue of selected papers from the 13th International Symposium on Numerical Analysis of Fluid Flow, Heat and Mass Transfer — Numerical Fluids 2018
- Author
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Eric Goncalves, Dia Zeidan, T. E. Simos, Ashoke De, and Charis Harley
- Subjects
Computational Mathematics ,Computational Theory and Mathematics ,Modeling and Simulation ,Mass transfer ,Numerical analysis ,Fluid dynamics ,Mechanics ,Mathematics - Published
- 2021
40. Extraction of nonlinear elastic parameters of paper from the amplitude-dependent frequency response of cantilever beams
- Author
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Isaias Cueva-Perez, Roque Alfredo Osornio-Rios, Ion Stiharu, and Angel Perez-Cruz
- Subjects
Frequency response ,Materials science ,Cantilever ,Applied Mathematics ,Mechanical Engineering ,Linear elasticity ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Vibration ,Mechanical system ,Nonlinear system ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,Dynamic loading ,Nonlinear resonance ,0210 nano-technology - Abstract
In recent years, paper has been used as an alternative to traditional substrate materials in the development of strain sensors and accelerometers due to its flexibility, disposability due to environment low footprint and low cost. A lack of knowledge about the sources of nonlinearity in the mechanical behavior of paper makes difficult to consistently predict its performance. The characterization procedures available in the literature are based on both static and dynamic loading as a first attempt to describe the elastic behavior of paper in sensing applications. However, these procedures do not reveal the necessary information to describe the elastic behavior of paper under dynamic excitation. In this work, the nonlinear dynamic response of a harmonically excited paper-based cantilever beam is studied. A lumped model with a quadratic nonlinearity is adopted to describe the nonlinear response of paper-based cantilever beams. The obtained results show that the nonlinear resonance frequency response is dependent on the intrinsic properties of paper when discarding hygrothermal variations of paper as the main source of nonlinear behavior. It was found that the estimation of two nonlinear elastic parameters, α p (hysteresis nonlinear parameter) and E 0 (linear elastic modulus) could yield an improved description of the elastic behavior of paper subjected to vibrations. It was concluded that the existing paper characterization standards should be adapted to better predict the dynamic behavior of paper-based mechanical systems. Different types of paper materials were analyzed to study the influence of the intrinsic characteristics of paper on the nonlinear parameters.
- Published
- 2019
41. Dynamics of stain growth from sessile droplets on paper
- Author
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Joseph D. Berry, Gil Garnier, Michael J. Hertaeg, and Rico F. Tabor
- Subjects
Materials science ,Capillary action ,Kinetics ,02 engineering and technology ,Mechanics ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Stain ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Surface tension ,Colloid and Surface Chemistry ,Sessile droplet ,Growth rate ,Boundary value problem ,Wetting ,0210 nano-technology - Abstract
Hypothesis The rate of stain growth of a sessile droplet deposited on paper has been previously studied (Kissa, 1981; Danino and Marmur, 1994; Kawase et al., 1986; Borhan and Rungta, 1993) but is not fully understood. In particular, the mechanism by which the abrupt decrease in growth rate occurs is unknown. This process is expected to follow a model where the disappearance of the droplet is represented by a change to the boundary condition at the droplet-paper interface when the volume of the fluid inside the paper is equal to the volume of the simulated droplet. Experiments The stain size of sessile droplets on paper was monitored against time. A series of fluids varying in surface tension and viscosity was studied. The kinetics of stain growth was modelled and compared with experiments and existing models of stain growth. Findings The measured stain area formed by a sessile droplet deposited on paper follows a two regime mechanism (Danino and Marmur, 1994). In the initial regime, the dynamics are governed by the filling of pores. However, in the later stage, the process is influenced by the emptying/redistribution of fluid. Simulations show that experimental results are well described by a model that identifies the change in boundary conditions after the droplet is no longer present above the paper, coupled with the change to a redistribution dominated mechanism.
- Published
- 2019
42. Simulating the hygroexpansion of paper using a 3D beam network model and concurrent multiscale approach
- Author
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Artem Kulachenko and Hamid Reza Motamedian
- Subjects
Pointwise ,Deformation (mechanics) ,Computer science ,Applied Mathematics ,Mechanical Engineering ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Thermal expansion ,Stress (mechanics) ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,Modeling and Simulation ,General Materials Science ,Fiber ,0210 nano-technology ,Microscale chemistry ,Beam (structure) ,Network model - Abstract
A number of problems associated with dimensional stability of paper products have to do with hygroexpansion in response to changes in humidity or moisture content. The main underlying mechanism of hygroexpansion in paper is the effect of the change of fiber cross-sections transferred through fiber bonds. In fact, the transverse expansion of fibers can be an order of magnitude greater than the longitudinal expansion. Addressing such problems using modeling on the microscale is associated with large computational costs since both the bonds and the fibers need to be resolved. We present a method for modeling the hygro or thermal expansion of interconnected fiber networks modeled with beam elements and connected through beam-to-beam contact. Being a line structure, beams can only support pointwise contact, which poses a challenge for modeling the force transfer induced by the deformation of the cross-sections at the contact point. The idea of implementing the stress transfer is to use a concurrent multiscale approach in which the bond level is resolved in detail using the configuration of the fibers and the computed strains are passed over to the beam elements. We verify and prove the applicability of this approach by comparing it with continuum models. We demonstrate the advantage of using this approach in terms of its tremendous saving in time. The use of beam models for modeling the hygro- or thermal expansion of fiber networks enables considering relevant sizes in the problems involving dimensional stability, in particular those associated with embedded inhomogeneities. We will show the applicability of the model by providing insights into published experimental observations on the hygroexpansion properties of paper products. Finally, we will demonstrate that the use of a 2D model to simulate the inter-fiber bonds in a network, not only leads to underestimation of out-of-plane deformations, but also to overestimation of the contribution of the transverse deformation of fibers to the in-plane dimensional change of the network.
- Published
- 2019
43. Foundations of Information Science Selected papers from FIS 2002
- Author
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Pedro C. Marijuán
- Subjects
Information Science ,Reductionism ,Mechanics ,Bioinformation ,Adaptability ,Entropy ,Symmetry ,Science ,Astrophysics ,QB460-466 ,Physics ,QC1-999 - Abstract
The accompanying papers in the first issue of Entropy, volume 5, 2003 were presented at the electronic conference on Foundations of Information Science FIS 2002 (http://www.mdpi.net/fis2002/). The running title of this FIS e-conference was THE NATURE OF INFORMATION: CONCEPTIONS, MISCONCEPTIONS, AND PARADOXES. It was held on the Internet from 6 to 10 May 2002, and was followed by a series of discussions –structured as focused sessions– which took place in the net from 10 May 2002 until 31 January 2003 (more than 400 messages were exchanged, see: http://fis.iguw.tuwien.ac.at/mailings/). This Introduction will briefly survey the problems around the concept of information, will present the central ideas of the FIS initiative, and will contrast some of the basic differences between information and mechanics (reductionism).
- Published
- 2003
- Full Text
- View/download PDF
44. On the role of moisture in triggering out-of-plane displacement in paper: from the network level to the macroscopic scale
- Author
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C.G. van der Sman, Marc G.D. Geers, B.A.G. Lomans, Ron H. J. Peerlings, E. Bosco, Applied Mechanics and Design, Mechanics of Materials, Mechanical Engineering, and Group Geers
- Subjects
Paper ,Work (thermodynamics) ,Materials science ,Bending (metalworking) ,Constitutive equation ,FOS: Physical sciences ,02 engineering and technology ,Instability ,0203 mechanical engineering ,General Materials Science ,Composite material ,Anisotropy ,Multi-scale ,Condensed Matter - Materials Science ,Deformation (mechanics) ,Moisture ,Buckling ,Applied Mathematics ,Mechanical Engineering ,Materials Science (cond-mat.mtrl-sci) ,Hygro-mechanics ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,020303 mechanical engineering & transports ,Out-of-plane bending ,Mechanics of Materials ,Macroscopic scale ,Modeling and Simulation ,Fibrous network ,0210 nano-technology - Abstract
The response of paper to humidity variations is a complex, inherently multi-scale problem. The hygroscopic swelling of individual fibres and their interactions within the fibrous network govern the macroscopic, sheet-level response. At this scale, moisture induced instabilities and out-of-plane deformations may occur, which are critical for a number of industrial applications. This work specifically focuses on several aspects of this important issue. A macroscopic phenomenological hygro-mechanical model is first proposed, which aims at predicting moisture induced out-of-plane deformations in paper sheets. The constitutive model is based on the relation between these deformations and typical irreversible phenomena associated to the history of paper manufacturing, i.e. the release of dried-in strains. The model is used to describe bending induced by moisture gradients through the thickness of the sheet as well as buckling due to moisture variation in the presence of mechanical constraints. The results of the model show that the anisotropic sheet-level hygro-expansion has a strong influence on the instability phenomena. Moreover, a comparison with experiments provides adequate semi-quantitative estimates. An additional step is made towards the multi-scale understanding of paper hygro-mechanics. The fundamental physical mechanisms governing the macroscopic moisture induced response are investigated on the basis of the underlying fibrous network. To this aim, a meso-structural model is developed which consists of a network of fibres randomly positioned in a planar region according to an orientation probability density function. A series of network simulations reveals that upon moisture content variations the expansion of the inter-fibre bonding regions essentially drives the overall deformation. Particularly in the case of anisotropic fibre orientation, this explains the origin of the macro-scale anisotropic hygro-expansion, which is essential for the observed sheet-level instability phenomena.
- Published
- 2016
45. Droplet Imbibition into Paper Coating Layer: Pore-Network Modeling Simulation
- Author
-
Yin, X., Aslannejad, H., de Vries, E. T., Raoof, A., Hassanizadeh, S. M., Hydrogeology, Environmental hydrogeology, Hydrogeology, and Environmental hydrogeology
- Subjects
Materials science ,General Chemical Engineering ,Imbibition ,0208 environmental biotechnology ,02 engineering and technology ,Droplet penetration ,engineering.material ,Article ,Catalysis ,Physics::Fluid Dynamics ,Coating ,Pore-network model ,Mechanics ,Penetration (firestop) ,021001 nanoscience & nanotechnology ,020801 environmental engineering ,Volumetric flow rate ,Paper coating layer ,engineering ,Chemical Engineering(all) ,Richards equation ,Wetting ,0210 nano-technology ,Material properties ,Porous medium - Abstract
Liquid penetration into thin porous media such as paper is often simulated using continuum-scale single-phase Darcy’s law. The underlying assumption was that a sharp invasion front percolates through the layer. To explore this ambiguous assumption and to understand the controlling pore-scale mechanisms, we have developed a dynamic pore-network model to simulate imbibition of a wetting phase from a droplet into a paper coating layer. The realistic pore structures are obtained using the FIB-SEM imaging of the coating material with a minimum resolution of 3.5 nm. Pore network was extracted from FIB-SEM images using Avizo software. Data of extracted pore network are used for statistically generating pore network. Droplet sizes are chosen in the range of those applicable in inkjet printing. Our simulations show no sharp invasion front exists and there is the presence of residual non-wetting phase. In addition, penetration of different sizes of droplets of different material properties into the pore network with different pore body and pore throat sizes are performed. We have found an approximately linear decrease in droplet volume with time. This contradicts the expected \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sqrt{t}$$\end{document}t-behavior in vertical imbibition that is obtained using macroscopic single-phase Darcy’s law. With increase in flow rate, transition of imbibition invasion front from percolation-like pattern to a more sharper one with less trapping of non-wetting phase is also reported. Our simulations suggest that the single-phase Darcy’s law does not adequately describe liquid penetration into materials such as paper coating layer. Instead Richards equation would be a better choice.
- Published
- 2018
46. A Review Paper on: Containment Test and Impeller Burst Simulation using Explicit Dynamics
- Author
-
Priti Sawaikar
- Subjects
Impeller ,Containment ,Computer science ,Dynamics (mechanics) ,Mechanics ,Test (assessment) - Published
- 2019
47. The Characterization of Energy Absorption and Failure Response of Square Paper Tube by Quasi Static Axial Compression Test
- Author
-
Jie-Shing Lo
- Subjects
Materials science ,Energy absorption ,Axial compression ,Tube (fluid conveyance) ,Mechanics ,Quasistatic process ,Square (algebra) ,Characterization (materials science) - Published
- 2021
48. Flow of liquids through paper
- Author
-
Brendan D. MacDonald
- Subjects
Materials science ,Mechanical Engineering ,Microfluidics ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Matrix (mathematics) ,Flow (mathematics) ,Mechanics of Materials ,0103 physical sciences ,0210 nano-technology ,Porous medium - Abstract
The flow of liquids through paper is challenging to model due to the complexity and disordered layout of the fibre matrix. The expanding use and capability of microfluidic paper-based analytical devices ($\unicode[STIX]{x1D707}$PADs) and their requirement for precision has increased the need to accurately predict the flow of liquids through paper. Many studies have developed models and revealed some of the physical mechanisms responsible for the flow behaviour, but we still lack a complete understanding, particularly in relation to how the fluid fills the various voids with a wide range of shapes and sizes in the fibre matrix of paper. In the featured article, Chang et al. (J. Fluid Mech., vol. 845, 2018, 36–50) used a combined experimental and theoretical approach to uncover the importance of the liquid filling the intra-fibre pores, showed that this results in deviation from the flow behaviour predicted by the Lucas–Washburn equation and developed a model which accounts for this effect.
- Published
- 2018
49. Mathematical model for mixing in a paper-based channel and applications to the generation of a concentration gradient
- Author
-
Simon Song, Ilhoon Jang, and Gangjune Kim
- Subjects
Fluid Flow and Transfer Processes ,Materials science ,Field (physics) ,Mechanical Engineering ,010401 analytical chemistry ,Flow (psychology) ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Sample (graphics) ,0104 chemical sciences ,Front velocity ,0210 nano-technology ,Constant (mathematics) ,Porosity ,Mixing (physics) ,Communication channel - Abstract
A paper-based channel is a useful platform for the facile development of analytical devices implementing various chemical or biological reactions. To improve the analytical performance for various applications, it was necessary to analyze the detailed mixing characteristics within a paper-based channel. In this paper, we proposed a mathematical model to predict a concentration field created as a result of the imbibition of multiple fluids within a porous material. Interestingly, we found that the model exhibited a constant interdiffusion width within a paper-based channel even though the flow front velocity decreased over time. We were able to verify that our model accurately predicted the concentration field by comparing the experimental and numerical results for mixing in a 2 inlet-channel. Finally, we designed and fabricated paper-based channels to generate two (linear and non-linear) concentration gradients based on predictions made by the model. Both the experimental and numerical results were in good agreement, demonstrating that our model was accurate and useful for developing a paper-based analytical device utilizing the mixing characteristics of a sample and reagent flow system.
- Published
- 2018
50. Comments on the paper 'Impact of temperature dependent heat source and non-linear radiative flow of third grade fluid with chemical aspects'
- Author
-
Mohamed M. Awad
- Subjects
Physics ,Nonlinear system ,nema ,Flow (mathematics) ,Renewable Energy, Sustainability and the Environment ,lcsh:Mechanical engineering and machinery ,Radiative transfer ,lcsh:TJ1-1570 ,Mechanics - Abstract
The current discussion is presented to increase the awareness among the readers of the journal Thermal Science. Comments are presented in particular on the paper by Hayat et al. [1] where the authors investigated effect of non-linear radiative flow of third grade fluid and temperature dependent heat source with chemical aspects. The current discussion concerns some questionable results included in the aforementioned paper.
- Published
- 2019
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