Search

Efforts to model the human upper respiratory system have undergone many phases. Geometrical proximity to the realistic shape has been the subject of many research projects. In this study, three different geometries of the trachea and main bronchus were modelled, which were reconstructed from computed tomography (CT) scan images. The geometrical variations were named realistic, simplified and oversimplified. Realistic refers to the lifelike image taken from digital imaging and communications in medicine format CT scan images, simplified refers to the reconstructed image based on natural images without realistic details pertaining to the rough surfaces, and oversimplified describes the straight wall geometry of the airway. The characteristics of steady state flows with different flow rates were investigated, simulating three varied physical activities and passing through each model. The results agree with previous studies where simplified models are sufficient for providing comparable results for airflow in human airways. This work further suggests that, under most exercise conditions, the idealised oversimplified model is not favourable for simulating either airflow regimes or airflow with particle depositions. However, in terms of immediate analysis for the prediction of abnormalities of various dimensions of human airways, the oversimplified techniques may be used. [ABSTRACT FROM PUBLISHER]

In this research, the rheological properties and flow behaviour of M2 high-speed steel have been investigated in low and high solid fractions by compression and rheometry tests. First series of experiments were started by partial remelting of rolled-annealed M2 billet in an argon-controlled atmosphere and holding for an appropriate time to obtain a globular microstructure and then conducting the rapid compression test on the prepared sample. Load versus deformation data were recorded using a high-frequency data acquisition system during the tests. Deformation mechanism of the semi-solid steel alloy and its correlation to rheological properties were then investigated. In the second series of experiments, the material was sheared continuously while cooling down from liquidus state to a semi-solid temperature. The rheology tests were performed using a self-developed concentric cylindrical viscometer under different cooling rates (25 °C/min–35 °C/min) and shear rates. The results revealed that when solid fraction exceeds about 40%, the viscosity increases suddenly and reaches a viscosity of about 20 Pa s. This solid fraction is a critical point when designing the process for industrial applications such as thixocasting. [ABSTRACT FROM PUBLISHER]

Sheet-bulk metal forming is a new class of sheet forming technology with intended three dimensional material flows as bulk forming process. This new technology usually comprises several traditional forming processes, such as drawing, upsetting, ironing, etc. which exhibits different strain states. The flow behaviours of 2024 aluminium alloy sheet in hot tension and compression were paid attention considering the effect of forming parameters including temperature and initial strain rate in this paper. By regression analysis, the values of deformation activation energy of different processes were calculated. To determined reasonable forming parameters for sheet-bulk metal forming, the power dissipation map and instability map were established based on dynamic materials model theory. [ABSTRACT FROM AUTHOR]

The rheological properties, microstructure, textural properties, colour and droplet size distribution of mayonnaise-like emulsion models prepared using 10–30 wt.% of palm olein-based diacylglycerol (POL-DAG) oil were compared with those of the control (100 wt.% VCO) model. There were significant ( P < 0.05) differences in the particle size distribution of the oil droplets, the textural properties, and the rheological properties of the various emulsion models. The rheological analysis included the determination of the flow curves, yield stress, thixotropy, apparent viscosity, and viscoelastic parameters. The concentrated oil-in-water (O/W) emulsion with 30 wt.% POL-DAG substitution exhibited high thixotropy. The POL-DAG content had a substantial effect on the rheological properties of yield stress, storage modulus ( G′ ) and loss modulus ( G″ ). The pseudoplastic behaviour of the emulsions was demonstrated. The size of the particles in the 30% POL-DAG-substituted emulsion was dramatically increased after one day and 30 days of storage. All of the emulsion samples with POL-DAG substituted for VCO showed a relatively non-uniform bimodal droplet size distribution after one day of storage. In general, substitution of 10–20 wt.% POL-DAG oil is appropriate for preparing O/W emulsions that had flow curves and textural properties similar to those of the control sample. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a rotating membrane emulsification setup incorporating a 6.1μm pore diameter SPG membrane was used to produce O/W emulsions of average droplet sizes between 23.4 and 216.6μm. All emulsions consisted of 10vol% of sunflower oil or silicone oil stabilised by 1wt% Tween 20. The transmembrane pressure (0.1–1.8bar), rotational speeds (100–2000RPM) annular gap width (5–45mm), dispersed and continuous phase viscosity were all investigated as to their effect on emulsion droplet size and dispersed phase flux. Modification of the dispersed phase flow properties alters the droplet size with four regions being suggested; a decrease in size (as droplet coalescence is minimised), a plateau (size-stable zone), a gradual increase in size (due to transfer of mass via droplet neck) and then a rapid increase (due to jetting). The importance of Taylor vortices development was seen with larger droplets formed in their absence; typically at low rotational speeds, narrow vessel diameters and more viscous continuous phases. It was concluded that the flow behaviour of each phase requires careful consideration to understand the likely formation mechanism(s) during operation. Across the pressure and viscosity ranges investigated, the dispersed phase flux ranged between 50 and 12,500Lm−2 h−1 and pore activity was within the range of 0.5–2.7%. [Copyright &y& Elsevier]

Highlights: [•] Capacitance time traces used to asses bend effect on two-phase flow. [•] Visual comparison of time traces showed effect downstream of the bend for slug flow. [•] Wavelet variance of the signals showed bend effect for intermittent and annular flow. [•] Bend effect was observed at least 21.5 tube diameters downstream of the bend. [Copyright &y& Elsevier]

Traditional Indian cereal based fermented food products like Kurdi (Maharashtra) and Seera (Himachal Pradesh) are prepared from batter of fermented wheat grains. These wheat batters were prepared by soaking wheat grains (Triticum Astivum L., variety: PBN51) in water at different temperatures (30, 37.5 and 45°C) for four days (natural fermentation), crushed, centrifuged and characterized for rheological properties. The present study was aimed to test the effect of soaking temperature (during natural fermentation of wheat grains) on the rheological behavior of wheat batter. It was determined that viscosity and yield stress of the wheat batter decreased with increase in soaking temperature of natural fermentation. Yield stress decreased by 65% and 82% for wheat grains soaked at 37.5°C and 45°C, respectively as compared to those soaked at 30°C. This was attributed to the degradation of the carbohydrates by the natural flora of microorganisms. Increasing the soaking temperature during natural fermentation decreased the fluid consistency index and increased the flow behavior index of the batter, demonstrating a lower viscosity and increased fluidity. All the samples revealed shear thinning behavior. Gelatinization temperature of the wheat batter decreased with increase in soaking temperature as demonstrated by viscoelastic analysis (loss modulus, storage modulus, Tan δ) of the samples. [ABSTRACT FROM AUTHOR]

Ethylene Propylene Diene Monomer (EPDMJ rubber emerges as a dominant elastomer for major engineering applications. The major properties of EPDM are its outstanding heat, ozone and weather resistance ability. It has a good resistance to polar substances and steam condition too. In automobiles EPDM rubber has a common use as seals. This includes door seals, window seals, trunk seals and sometimes hood seals. Frequently these seals are the source of noise due to the movement of the door versus the car body. This is due to friction between the EPDM rubber parts and the mating surfaces. Thus, the contact iteration between the rubber sealing and the indenting object must be known to optimize the performance of rubber sealing. However, it is need less to mention that the behaviour of any viscoelastic material is very difficult to be predicted. In the present work various tribo-characteristics of EPDM rubber of different hardness have been evaluated utilizing the available laboratory test facilities in the jadavpur University, Kolkata, India. Compression tests have been carried out using 'Instron' to determine the flow behaviour of EPDM rubber of different hardness both in dry as well as under different conditions of lubrication. The flow behaviour like load -vs.- elongation curves, true stress -vs.- elongation curves and true stress -vs.- true strain curves have been drawn from the experimental data. Abrasive wear behaviour has been evaluated using a two-body abrasion tester and the pattern abrasion has been appraised through SEM/EDAX study. Experimental results reveal that the hardness of EPDM rubber has significant effect on the flow behaviour and wear characteristics. The hardness, again, depends on the proportion of carbon black (CB) content. Thus it can be stated that the flow behaviour can be governed by controlling the CB concentration in the EPDM rubber. Based on the experimental results conclusion has been drawn accordingly. Some of the important tribo-characteristics of EPDM have been highlighted. Light has also been shed on various possible areas of further researches those should be undertaken in the future to come. [ABSTRACT FROM AUTHOR]

Abstract: Flow behaviour of a Nickel Aluminium Bronze (NAB) alloy under hot compressive deformation was investigated using a deformation dilatometer. Temperatures of 1023, 1073, 1123 and 1173K and strain rates of 0.1, 1.0 and 10s−1 were used as the forming parameters. The experimental results showed that true stress–strain curves of the alloy exhibited dynamic recovery and dynamic recrystallisation with single-peak stress. Dynamic recovery was dominant at higher temperature and lower strain rate. The peak stress increased as the strain rate and temperature increased. The peak strain also increased with increasing strain rate. However, it was independent of temperature. The flow curves can be represented by the hyperbolic-sine law Arrhenius equation with activation energy of 514.25kJ/mol. Comparisons between predicted flow stresses and experimentally determined results showed that the developed constitutive models were sufficiently accurate to demonstrate flow behaviour at high temperatures of the NAB alloy. This was supported by a correlation coefficient R of 0.981 and an average relative error of 13.42% for the particular test conditions. Dynamic material modelling approach has been used to describe flow stability/instability. For the NAB alloy, the criterion of the strain rate sensitivity, the criterion with regard to the variation of strain rate sensitivity with log and the criterion of the temperature sensitivity were always satisfied. The critical criterion is the rate of change of the temperature sensitivity with respect to log . [Copyright &y& Elsevier]

The objective of the present work is to generate general rheological criteria to investigate high solid loading dispersions suitable for the shaping of homogeneous ceramic bodies. Systematic analysis of the rheological properties of moderately low specific surface area (SSA) Ce0.9Gd0.1O3-δ (CGO10) dispersions was performed in rotational and oscillatory modes. The dispersant content was optimized to attain fully stabilized dispersions. A critical upper limit for the ceramic content was introduced and denoted ϕ h. It defines the limit to non-Newtonian flow and corresponds to the highest feasible volume fraction to which reproducible dispersions are achieved. The method proposed for its determination is based on the analysis of the flow index as function of the ceramic volume fraction. For the CGO dispersions formulated in this work, ϕ h was found to be around (0.34±0.04). The maximum volume fraction (ϕ m) was also estimated and found to be (0.55±0.01). [ABSTRACT FROM AUTHOR]

[Display omitted] • The GPU-based DEM approach is used to study the lab-scale die filling system. • The numerical model is calibrated and validated well with experimental data. • The stirrer occupying a specific space and reducing the effective discharge area. • Flow patterns of the free-flowing powder during die filling process is analyzed. Understanding die filling behaviour of powders is critical in developing optimal formulation and processes in various industries, such as pharmaceuticals and fine chemicals. In this paper, forced die filling is analysed using a graphics processing unit (GPU) based discrete element method (DEM), for which a powder feeder equipped with a wired stirrer is considered. The influences of operating parameters, such as the initial powder bed height, the filling speed, and the stirrer speed, on the die filling performance are systematically explored. It is shown that a larger initial powder bed height leads to a higher filling ratio, which can be attributed to a higher filling intensity; while the deposited particle mass in the die is almost independent of the powder bed height, when the initial fill level is larger than a critical bed height. Additionally, the filling ratio slightly increases with the increase of stirrer speed for cases with a stirrer, while the filling ratios are lower than that without a stirrer, which is attributed to the stirrer occupying some space above the die and reducing the effective discharge area. The obtained results can provide useful information for optimising the feeder system design and the operating condition. [ABSTRACT FROM AUTHOR]

In the present work, a constitutive model is developed to describe the flow behaviour of metastable Fe-18Cr-10Mn-0 ·39N (wt-%) austenitic stainless steel, considering deformed microstructure of the alloy as a composite material (mixture of austenite/α'-martensite). The results of previous studies are used to validate the model. It is shown that the developed model is more appropriate to predict flow behaviour of the metastable alloy undergoing considerable martensitic transformation during deformation when compared with the modified Ludwik equation suggested in some earlier works. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hot compression tests for as-cast AZ61 alloy without annealing were performed. [•] The apparent activation energy and the strain rate sensitivity were estimated. [•] The DRX kinetics can be well interpreted by the modified Avrami type equation. [•] DRX behaviour was investigated with reference to the microstructure observation. [ABSTRACT FROM AUTHOR]

A new integrated physically based constitutive model was developed for an age hardenable Al-Mg-Si alloy. The kinetics of precipitation during various stages of aging was modelled. The precipitate features consisted of particle radius and volume fraction obtained from the kinetics model, which was used to compute the alloy yield strength/hardness. A published multiinternal variable workhardening model was improved to take into account the effects of solute solution and precipitates on the alloy hardening capacity after performing different cycles of aging treatment. The flow curves and hardness predicted by the model were in good agreement with the experimental results. The model is able to predict the microstructure evolution such as cell/subgrain size and dislocation density in the cell interior during the plastic straining of material at different temper conditions. [ABSTRACT FROM AUTHOR]

Investigations were conducted employing a three-component constrained mixture design to formulate milk blends from soy milk, peanut milk and cow milk. Variations in chemical composition and physico-chemical properties of 10-soy-peanut-cow milk (SPCM) formulations were studied. Variations in soy-peanut-cow milk (SPCM) concentrations influenced to varying levels the chemical composition and physico-chemical properties of blends. SPCM formulations containing significant amounts of all three ingredients used (60-70% soy milk, 20-27% peanut milk and 7-20% cow milk) had high crude protein and fat values ranging from 2.20-2.51% and 5.00-6.35% respectively. Increasing soy concentrations caused relative increases in protein content while fat content increased with increasing peanut concentrations. SPCM formulations were high in the minerals Fe and Mn relative to cow milk which was high in Ca and Zn content. Trends in pH were contrary to titratable acidity and increased with increasing soy milk content but decreasing cow milk content. SPCM formulations demonstrated acceptable non-Newtonian behaviour and consistency indices. [ABSTRACT FROM AUTHOR]

Electric current pulse (ECP) was commonly applied to solidification process of Al melt to achieve fine solidification microstructure. In this paper, numerical simulation method was employed to analyse flow behaviour of the melt and the mechanism of ECP on the grain refinement during the solidification. The calculation results showed that the ECP led to fluctuation of the Al liquid surface, and the liquid flowed inward and down in a circular motion. The fluctuation and circular flow behaviour were caused by the forces including Lorentz force, surface tension and buoyancy. The results also revealed that the higher the frequency and peak value of the ECP, the larger the flow velocity was. On the other hand, the depth of the electrodes in the liquid had little influence on the convection flow of the liquid. In summary, our simulation results explained the refinement mechanism of the ECP on solidification microstructure and provided a novel and feasible approach to evaluate and optimise the structure refinement of the ECP. [ABSTRACT FROM AUTHOR]

Abstract: This work studied the flow behaviour of microfluidic-based acoustic sensor at a region where the flow of fluid was considered to be significant in determining the overall flow behaviour of the system flow in microchannel. The study was carried out based on finite element model (FEM) using ANSYS multiphysics package. Two structural parameters, reservoir or chamber height and the number of microchannel were used as the varying parameter. The flow behaviour was then analysed based on pressure distribution, velocity contour and velocity vector for a single and dual microchannel configuration with different reservoir height. The height was varied in the range of 20 to 100μm due to limitation in the thickness of mold material during fabrication. Simulation results reveal that the flow response was not critically affected by the chamber height, whereas the dual microchannel configuration had an approximately a factor of 2.8 higher in terms of its flow velocity compared to the single microchannel configuration. This effect was referred as an amplification factor of the flow response due to this structure variation. [Copyright &y& Elsevier]

The effects of pulsed electric field (PEF) treatments on rheological and colour properties of soy milk were evaluated. Flow behaviour, viscosity and rheological parameters of PEF-treated soy milk were monitored using a controlled stress rheometer. For PEF treatments, electric field intensity of 18, 20 and 22 kV cm− 1 and number of pulses of 25, 50, 75 and 100 were used. For the measurements of rheological properties of soy milk shear rates between 0 and 200 s− 1 was used. The rheological behaviour of control and the PEF-treated soy milk were described using a power law model. The PEF treatments affected the rheological properties of soy milk. Apparent viscosity of soy milk increased from 6.62 to 7.46 (10− 3 Pa s) with increase in electric field intensity from 18 to 22 kV cm− 1 and increase in the number of pulses from 0 to 100. The consistency index ( K) of soy milk also changed with PEF treatments. Lightness ( L**), red/greenness ( a**) and yellowness/blueness ( b**) of soy milk were affected by PEF treatments. [ABSTRACT FROM AUTHOR]

Experimental true stress-true strain data of Nimonic C-263 alloy in solution treated as well as aged condition have been analysed using different flow relationships. Ludwigson relationship provides the best fit of the data for all the conditions investigated. The transition in macroscopic flow behaviour of the alloy with plastic strain, in solution treated condition, can be correlated with the transition in deformation mode from low strain regime to high strain regime. Although aging does not appear to alter the macroscopic flow behaviour, it causes a considerable change in flow parameters of the Ludwigson relationship and substructural evolution. On the other hand, the effect of sheet thickness is marginal. The flow data of the aged alloys fitted according to Ludwigson model not only yield a unique set of flow parameters for each aging condition but also exhibit a systematic trend with aging time. The transition in macroscopic flow behaviour of the alloy with strain, in aged conditions, can be correlated with a change in dislocation mechanism from dislocation-precipitate interaction at lower strains to dislocation-dislocation interaction at higher strains leading to formation of a dense dislocation tangled networks in the matrix regions surrounding the precipitates. The alloy in both solution treated and aged conditions exhibits three fairly distinct stages of strain hardening. The strain hardening rate decreases in regime I, remains constant in regime II and begins to fall again in regime III. Furthermore, it is observed that the alloy specimen with longitudinal orientation (L, i.e. parallel to rolling direction), exhibits marginally highest strain hardening rates, while specimens with long transverse orientation exhibit lowest strain hardening rates both in solution treated and aged conditions. However, for all other in-plane orientations (i.e. L+30°, L+45° and L+60°), the strain hardening rate data are fairly very close and lie in between those of longitudinal and long transverse orientations. [ABSTRACT FROM AUTHOR]

In industrial sheet metal forming processes the complexity of parts has been increased within the last decade due to the demands on ambitious designs and lightweight construction. As the forming processes are often laid out near the limit of feasibility, small variations of process parameters and materials' properties may lead to an increased scrap rate in serial production. The consideration of varying parameters in the computerized process design is generally realizable, but especially the modelling of the material properties' variation in numerical simulation close to reality is not investigated comprehensively yet. The varying parameters considered in a so called stochastic simulation are often limited to the mechanical properties, which can be determined within the uniaxial tensile test. As within the forming process of a complex sheet metal part different stress states occur, the batch variation under different forming conditions has to be investigated in detail. Within this work a basic investigation for the consideration of the batch variation under different stress states is presented. Three coils of the same steel grade, the mild deep drawing steel DX56, are characterised experimentally in order to investigate the scatter band of the stresses between the three batches representing material variation close to reality. For this the flow behaviour is determined under uniaxial stress condition and under biaxial stress condition. Furthermore the results of the tests under biaxial stress condition lead to a batch specific biax-stress-point, which represents a further reference point for the yield locus interpolation according to Hill 90. The forming limit diagrams are determined experimentally for the three batches in order to reproduce scattering of the onset of necking as well. Based on the experimental results, three batch specific material models for FE-simulation are prepared and used as input parameters for numerical forming simulations. Using the cross die geometry with two different initial blank geometries, different stress states can be adjusted in four reference points, covering the stress states between uniaxial and biaxial stress condition, thus, the plane strain area. Within the reference points, the effect of materials' properties variation on the risk of failure is evaluated. [ABSTRACT FROM AUTHOR]

Abstract: Aqueous extractions (at 25°C) of flours from six Greek wheat cultivars that differed in their bread-making quality, followed by porcine pancreas α-amylase digestion to remove starch contaminants and precipitation with ammonium sulphate (saturation at 95%), yielded arabinoxylan isolates with notable differences in molecular weight, ranging from 146,500 to 397,000, and in arabinose-to-xylose ratios (Ara/Xyl, varying between 0.57 and 0.71). The arabinoxylan isolates contained only small amounts of proteins and were relatively free of other polysaccharide contaminants. Generally a very high ratio of trans to cis-ferulic acid content was detected for all samples. The genotype also had an impact on the molecular characteristics of these polysaccharides. 1H NMR spectroscopy revealed variations in the un-substituted (61.1–67.9%) and di- (19.4–28.1%) and mono-substituted xylose residues (10.0–16.6%). Using 2D NMR spectroscopy, it was feasible to identify the spin sequence of individual monosaccharide residues and elucidate their structure, despite the extensive overlapping of 1H and 13C resonances. Differences in the physicochemical properties of the arabinoxylans, such as the critical concentration values (c∗ and c∗∗), viscosity, shear-thinning behaviour, as well as the gelling ability, could not be fully explained by differences in molecular size and structure of the isolated polysaccharides. [Copyright &y& Elsevier]

Deformation behaviour and microstructures at failure were investigated in a mill cold worked 70∶30 α-brass over the test temperature range of 298-973 K and strain rate range of 10−5-5×10−3 s−1. Tensile properties as a function of temperature revealed three distinct regions, with their temperature sensitivity being maximum at intermediate temperatures (553-673 K) and much less towards the lower and higher temperature ranges. Two values of activation energy for high temperature deformation Q were obtained to be 117·5 kJ mol−1 below 623 K and 196·4 kJ mol−1 above this critical temperature. In the respective temperature range the values of stress exponent n were 5·6 and 3·8. Based on the values of Q and n, the deformation mechanism was suggested to be dislocation climb creep with a probable contribution from dislocation pipe diffusion on lowering the temperature. Both grain size and cavity size were found to increase with increasing test temperature, suggesting them to be interrelated and act as an alternative steps for accommodating grain boundary sliding. Static grain growth study, over the temperature range of 773 to 1073 K, led to activation energy for grain growth to be 71 kJ mol−1, with the time exponent of 0·37. [ABSTRACT FROM AUTHOR]

In this paper, flow over a circular cylinder with detached short splitter-plates is numerically simulated so as to assess the flow behaviour and its characteristics. A finite-volume solver based on the Cartesian-staggered grid is implemented. Furthermore, the ghost-cell method in conjunction with Great-Source-Term technique is employed to enforce directly the no-slip condition on the cylinder boundary. The accuracy of the solver is validated by simulation of the flow around a single circular cylinder. The results are completely compatible with the experimental data. Eventually, the flow over a circular cylinder with splitter-plate in its downstream in Re = 40, 100 and 150, 0 ≤ G/D ≤ 10, and 0 ≤ Z/D ≤ 1.25 (where D is the cylinder diameter, G and Z are the horizontal and vertical distances between leading edge of the splitter-plate and the cylinder base, respectively) are simulated and analysed. For these configurations that are being studied, the drag and lift coefficients, the Strouhal number and the flow visualising parameters are obtained. The same simulations are also performed for the cases where dual splitter-plates are in a parallel arrangement embedded in the downstream of the cylinder. These compounds can be applied in many mechanical types of equipment to minimise flow-induced forces and suppress periodic vortex shedding. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we investigated the rheological and magnetorheological behaviours of an extremely bidisperse (nano–micro) magnetizable fluid (sample D1) for comparison of a commercial magnetorheological fluid (MRF-140CG; LORD Co. (USA)) with the same magnetic solid volume fraction, using the Physica MCR-300 rheometer with a 20mm diameter plate–plate magnetorheological cell (MRD180). D1 sample is a suspension of micrometer range Fe particles in a transformer oil based magnetic fluid as carrier. For both types of samples, the experimental data for zero and non-zero magnetic field conditions were fitted to equations derived from the Newtonian and Cross type flow equations, as well as the Herschel–Bulkley model. The main advantage of both rheological equations for the quantitative description of the magnetic field behaviour of samples is that they can be used in regular CFD codes to compute the flow properties of the magnetorheological fluid and of the bidisperse magnetizable fluid for practical applications. [Copyright &y& Elsevier]

Abstract: The flow behaviour of aqueous solutions of gelatin, and skim milk–gelatin mixtures treated by high-pressure processing (HPP) were investigated. HPP was carried out at 5°C for 15min, at 150MPa, 300MPa, 450MPa and 600MPa, and the gelatin concentrations were varied from 0 to 1wt.%. Viscosity measurements showed that the HPP treatment did not affect the flow behaviour of gelatin alone, nor that of the skim milk–gelatin mixtures made with <0.4wt.% gelatin. However, at gelatin concentration >0.4wt.%, the mixtures treated with 300 and 450MPa exhibited a peculiar flow behaviour, where at intermediate shear rates the viscosity was higher than that of the non-treated mixture or the mixtures treated at 150MPa and 600MPa. Particle size measurements showed that for gelled mixtures (>0.4wt.% gelatin) 300MPa HPP treatment resulted in an increase in the particle size, while at all other pressure treatments (>150MPa), a shift in particle size distribution to lower sizes was observed. Confocal microscopy showed that these skim milk–gelatin mixtures were phase-separated with a gelatin continuous phase, this was confirmed by dynamic rheological measurements which showed that qualitatively the viscoelastic properties of the mixtures were the same. A mechanism of the effect of high-pressure treatment on the casein micelle in skim milk–gelatin mixtures is proposed. Industrial relevance: This fundamental work, dealing with the effect of high pressure on the physicochemical properties skim milk–gelatin mixtures could be relevant to the industry in several ways. Firstly, skim milk–gelatin mixtures are widely used in the dairy industry, particularly in yoghurt manufacture, where gelatine is used as a stabiliser. In addition the application of High Hydrostatic Pressure to such a system is also relevant, as this technology could be used as a substitute to the conventional heat treatment processes. Secondly, an important finding of this study is that under certain conditions of high pressure and gelatine concentration, an increase in viscosity is observed at intermediate shear-rate (between 10 and 100s− 1). This is highly relevant to Industry if the system requires subsequent pumping. Thirdly, from a sensory view point, this range of shear rates (10 and 100s− 1) is comparable to that experienced by a food bolus during swallowing. Thus, this effect of high pressure on the viscosity can influence sensory attribute of the skim milk–gelatin food system. [Copyright &y& Elsevier]

The objective of the work is related to the modelling of micro-cavities replication in polymer plates by the roll embossing process. Finite element simulations are set up and performed to analyse the polymer deformation and flow leading to the filling of micro-cavities engraved on the moving roll system in the roll to roll (R2R) process. In the proposed approach, the roll engraved with micro-cavities is assumed to be undeformable, whereas the polymer plate rigid exhibits a viscoelastic or a coupled viscoelastic-viscoplastic material behaviour depending on the experimental processing conditions. The flow behaviour of the selected materials (cyclic olefin copolymer, COC) depends on the experimental processing parameters (rolling velocity, applied pressure and temperature) that are considered. The numerical simulations are performed using LsDyna® finite element software in order to analyse the filling of the micro-cavities vs. the rolling velocity and temperature, as a function of friction and sliding conditions. The results lead to the choice of roll embossing conditions in order to get the micro-cavities with the required geometries and properties. [ABSTRACT FROM AUTHOR]

Abstract: Rheological properties such as flow behaviour, viscosity, viscoelasticity, and thixotropy of solutions of β-glucan purified from barley fibre concentrate and twelve commonly used food gums, alone and in combinations, were characterised using an oscillatory rheometer. Pure gums and gum combinations were evaluated at 0.5% and 0.75% (w/w) total gum concentration in aqueous medium, whereas the β-glucan/gum ratios were kept at 90/10 or 80/20 (w/w). Viscosity synergism was observed for β-glucan solutions in combination with xanthan, iota-carageenan, and carboxymethyl cellulose. However, barley β-glucan blends with lambda-carageenan, Konjac, high- and low-methoxyl pectin, microcrystalline cellulose, alginate, and gum arabic showed marked lowering of the viscosity compared to β-glucan alone. In addition, β-glucan/xanthan gum blends demonstrated improved shear tolerance compared to xanthan dispersions alone, and soft gel transformation. Non-thixotropic behaviour was observed for 0.5 and 0.75% (w/w) β-glucan dispersions and its gum combinations. None of the gum combinations studied demonstrated thixotropy. [Copyright &y& Elsevier]

Abstract: The pathway to reach a certain target in many processes such as bioleaching, due to the complex and poorly understood hydrodynamics, reaction kinetics, and chemistry knowledge involved is not apparent. An investigation of the interactions between the parameters in bioleaching process can be applied to optimize the rate of metal extraction from sulphide minerals. Such investigations can be carried out with the aid of numerical simulations. In this study, a computational fluid dynamics (CFD) model was developed to better understand the mass transfer phenomenon and complex flow field around a single particle. The commercial software FLUENT 6.2 has been employed to solve the governing equations. Volume of fluid (VOF) method was used to predict the fluid volume fraction in a 3D geometry. The computational model has successfully captured the results observed in the experiments. Simulation results indicate that concentrations of species in a thin layer of liquid on the particle surface are much higher than their concentrations in the liquid bulk and significant gradients in the ion concentrations between the surface of the particle and the liquid bulk were observed. [Copyright &y& Elsevier]

The effect of the addition of different types of inulin (long-chain, native and short-chain inulin) at four concentrations (0, 2.5, 5 and 7.5% w/w) on flow properties of semisolid dairy desserts formulated with either skimmed or whole milk and three modified tapioca starch concentrations (2.5, 3.25 and 4% w/w) was studied. All samples displayed shear-thinning flow behaviour. The addition of the three types of inulin to whole milk samples with low starch concentrations (2.5 and 3.25% w/w) led to combined hysteresis loops: samples showed antithixotropy at low shear rate values, but thixotropy at high shear rate values. The remaining samples showed thixotropic behaviour. The effect of the different types of inulin on the flow properties was not only highly dependent on the inulin concentration but also on milk type and starch concentration. On adding 7.5% of long-chain inulin, which significantly increased consistency index values and significantly decreased flow index values in both types of milk and for all starch concentrations. [ABSTRACT FROM AUTHOR]

Abstract: Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10%w/v, 20°C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox–Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel–sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour. [Copyright &y& Elsevier]

(a) Absorbance spectra and (b) shear rate evolution of viscosity for the dry fig, jujube, pomegranate, date palm and concentrated grape vinegars. [Display omitted] • The quality of the vinegars was examined by spectroscopy and rheology techniques. • The effect of organic acids on UV spectrum and flow behaviour of vinegars was investigated. • Vinegars were found to exhibit non-Newtonian dilatant flow behavior. • Organic acid and phenolic compound concentration have an effect on vinegar quality. In this study, we focused on physical characterization and quality control of dry fig, jujube, pomegranate, date palm and concentrated grape vinegars using UV spectroscopy method and rheology technique. The optical spectra and flow behaviour of the vinegars were analysed in detail in the selected specific wavelength, shear rate and frequency ranges, respectively. It was determined that the peak values seen in the UV spectra of the vinegars were caused by the organic acid and phenolic compound concentration. The peak values in the UV spectra of the vinegars wavelength range of 190 nm to 240 nm and 250 nm to 300 nm were caused by the organic acid and phenolic compound concentration, respectively. In this context, it was predicted that concentrated grape vinegar, which has the highest absorbance value, has higher organic acid content and more antibacterial/antioxidant properties compared to the others. It is thought that the optical energy gaps of vinegars are related to the organic acid concentration and the release time. Flow properties of the vinegars were non-Newtonian thickening fluids (dilatant fluids) and compatible with the Power law model. The stable flow of the vinegars in the high shear rate region was interpreted as having a successful production process and being of good quality. [ABSTRACT FROM AUTHOR]

The viscosity of the concentrated black chokeberry juice has been studied at the soluble solids content of 50 - 67.8°Bx and the temperature range of 10 - 60°C. On the base of obtained results it was shown that concentrated black chokeberry juice exhibited Newtonian flow behaviour. The values of the viscosity strongly depended on the concentration and temperature and were in the range from 5.8 to 436.6 mPa s. To study the influence of soluble solids content on the viscosity, power-law and exponential functions were used. The effect of the temperature on the viscosity was described by the Arrhenius equation and the values of flow activation energy were in the range from 22.84 to 40.28 kJ/mol. Additionally, equations based on the Arrhenius and power-law or exponential functions describing combined effect of the soluble solids content and temperature on the viscosity were obtained. Because the values of flow activation energy strongly depended on the concentration, four parameters model for the concentrated black chokeberry juice was proposed. [ABSTRACT FROM AUTHOR]

Abstract: Retardation test, step-shear rate experiments, low-amplitude and large-amplitude dynamic measurements have been combined to study the nonlinear and time-dependent viscosity of dough and shear-induced effects of flow on dough structure. Despite large quantitative differences in linear viscoelastic constants, doughs from different flours or with different water contents display the same type of flow behaviour. Shear-induced structural changes cause flow to shift from a high viscosity steady-state regime to a low viscosity one. The process, irreversible, is responsible for the time-dependent character of dough viscosity and seems to be controlled by the mechanical energy absorbed. Nevertheless, the two steady-state viscosities follow the same shear-thinning flow curve, fitted by a Cross equation with an exponent close to 1; the Newtonian plateau is approached at very low shear rate values. Viscosity data obtained on different doughs yield a unique flow master curve in reduced coordinates. Shear-induced structural changes cause also the linear viscoelastic plateau modulus of dough to decrease; this progressive weakening of the network structure is irreversible and seems governed by the accumulated strain. These characteristics of dough rheology are discussed with reference to the behaviour of concentrated suspensions. [Copyright &y& Elsevier]

Abstract: The hydraulics of pitcher irrigation in saline water condition was studied in laboratory conditions in terms of flow behaviour of pitcher, soil moisture distribution, wetting front advance and distribution of salt concentration in the soil using different pitcher making materials. The Pitcher Type 1 (PT1) made up of local soil and sand yielded the lowest mean hourly depletion ranging from 0.42 to 0.62% depending on salinity of the water used. It was followed by PT2 made up of local soil, sand and resinous material with a mean hourly depletion of 0.51–0.69% and PT3 with local soil, saw dust and sand with a mean hourly depletion of 0.91–1.02%. In all cases, with the increase in salinity level of the water used (ranging from 5 to 20dS/m), the depletion rate and moisture content in the soil profile were found to decrease. Similarly, it was found that PT1 yielded the lowest wetting front advance and salt movement followed by PT2 and PT3. It was observed that the wetting front advance in the soil decreased with increasing salinity level of the water. The salt concentration in the soil was minimum near the pitcher and maximum at the soil surface and periphery of the wetted zone. In case of PT1, the maximum salt concentration in the soil profile ranged between 1.09 and 3.88dS/m using water with a salinity ranging from 5 to 20dS/m, respectively. Similarly, for PT2 the maximum salt concentration in the soil profile also ranged from 1.09 to 3.88dS/m and for PT3 from 2.30 to 6.07dS/m. A paired t-test revealed that the moisture as well as the salt distribution of PT3 differed significantly from PT1 and PT2 at α =0.05. Even, if the salt concentration remained the same and the moisture content remained within field capacity for PT1 and PT2, PT1 is preferred in comparison to PT2 and PT3 as the pitcher material of PT1 is locally economically available. [Copyright &y& Elsevier]

The article presents experimental methods for the analysis of material properties according to the typical time-temperature characteristics of the hot stamping process of ultra-high strength steels. The authors introduce a phenemenological approach to mathematically describe the flow behavior of the steel 22MnB5 in the austenitic state in dependency of temperature and strain rate. They discuss the thermal boundary conditions during hot stamping and the heat transfer between tool and workpiece.

A non-biodegradable polyhedral oligomeric silsesquioxane (POSS) nanocomposite biopolymer has been developed for fabrication of medical devices and for tissue engineering human organs. The polymer in solution, containing 2 wt% of POSS, has been synthesized, characterized and investigated to determine its key rheological properties. Thus, the variation of shear stress and viscosity as a function of shear rate has been determined at ambient temperature to estimate yield stress and the index of pseudoplasticity, respectively. The temperature dependence of viscosity and the effect of ageing on the viscosity of the polymer have also been investigated. Results are compared with those of a conventional polycarbonate urethane (PCU) polymer solution. The POSS-PCU polymer solution shows near-Newtonian behaviour in the shear rate range to 1000 s-1, having an apparent viscosity of ~3000 mPa s and a pseudoplasticity index of 0.90, decreasing slightly as the polymer solution is aged over 9 months. The temperature dependence of viscosity of the POSS polymer is extremely low and does not change with ageing but the yield strength increases from 2.7 Pa to 8.3 Pa. [ABSTRACT FROM AUTHOR]

Abstract: The effects of the addition of different types of inulin (oligofructose, native and long chain) at different concentrations (2%, 4%, 6%, 8% and 10%, w/w) on the flow behaviour of milk beverages model systems were studied. The flow of the inulin–milk solutions was Newtonian, except for whole milk samples with higher long chain inulin concentrations (8% and 10%), which were shear thinning. All inulin-κ-carrageenan–milk samples were shear thinning. The viscosity of 3.1% fat whole milk could be approximated by skim milk with 4–10% short chain inulin, or with 6–8% native inulin or with 4–6% long chain inulin. In κ-carrageenan–milk samples the addition of inulin could not replace the effect of milk fat on the viscosity of these systems. [Copyright &y& Elsevier]

The microstructure and mechanical properties of Incoloy A-286 forgings are sensitive to thermomechanical processing. In this research the hot deformation behaviour of A-286 superalloy is characterised in the temperature range of 1000–1100°C and strain rate range of 0·001–0·1 s-1 using the compression tests in order to develop a correlation between the grain size and the process parameters. It is found that at a strain rate of 0·001 s-1 in the temperature range of 1000–1100°C and at a strain rate of 0·01 s-1 in the temperature range of 1050–1100°C, the material exhibits dynamic recrystallisation (DRX), while at a strain rate of 0·01 s-1 and at the temperature of 1000°C and at a strain rate of 0·1 s-1 and in the temperature range of 1000–1100°C, the alloy exhibits the dynamic recovery (DR). [ABSTRACT FROM AUTHOR]

Response surface methodology was used to establish a relationship between total solids content, milk base, heat treatment temperature, and sample temperature, and consistency index, flow behaviour index, and apparent viscosity of plain stirred yogurts. Statistical treatments resulted in developments of mathematical models. All samples presented shear thinning fluid behaviour. The increase of the content of total solids (9.3-22.7 %) and milk base heat treatment temperature (81.6-98.4 °C) resulted in a significant increase in consistency index and a decrease in flow behaviour index. Increase in the sample temperature (1.6-18.4 °C) caused a decrease in consistency index and increase in flow behaviour index. Apparent viscosity was directly related to the content of total solids. Rheological properties of yogurt were highly dependent on the content of total solids in milk. [ABSTRACT FROM AUTHOR]

Abstract: The effect of inulin addition on the rheological and sensory properties of fat-free dairy desserts containing different starch concentrations (2.5%, 3.25% and 4%) was compared with the properties of full fat milk samples. All samples showed a thixotropic and shear-thinning flow behaviour. Hysteresis loops of inulin–skimmed milk samples were similar to those of whole milk samples without inulin. Skimmed milk samples showed lower consistency and lower shear thinning than either whole milk or inulin–skimmed milk samples. Inulin addition increased both storage modulus and complex viscosity values and decreased loss angle tangent value, except in the 4% starch sample. Adding inulin to fat-free dairy model desserts increased sweetness, thickness and creaminess. At low starch concentrations, inulin–skimmed milk desserts were perceived as sweeter, with more vanilla flavour and with the same thickness as whole milk desserts, but at 4% starch, the latter were thicker and creamier. [Copyright &y& Elsevier]

Abstract: Most of the investigations on foam concrete in the past have been confined to neat cement paste, cement paste with partial replacement with admixtures and to cement–sand mixes. This paper reports the results of a systematic study to ascertain the influence of filler type (i.e., sand and fly ash) and the particle size of sand on the properties of moist cured foam concrete. This study shows that the consistency of mixture, for achieving pre-formed foam concrete of design density, mainly depends on the filler type. The flow behaviour of foam concrete is mainly influenced by the foam volume. A reduction in particle size of sand caused an improvement in strength of foam concrete. For a given density, replacement of sand with fly ash resulted in higher strength. Finer filler resulted in a higher ratio of strength to density. [Copyright &y& Elsevier]

Abstract: The cereal dietary fibre β-glucan has outstanding functional and nutritional properties, because of its viscosity in aqueous systems and in the intestinal tract. The rheological behaviour of β-glucan (concentrations: 2% and 4%) isolated from extruded and autoclaved oat meal and from oat bran was evaluated using oscillatory and rheological measurements. In frequency sweep, the storage and loss moduli G′ and G″ of β-glucan preparations from extruded meal and from bran increased continuously with increasing frequency, showing a dominantly viscous behaviour. With increasing frequency, the elastic properties improved. β-Glucan from autoclaved meal also showed elastic behaviour. With the exception of β-glucan from autoclaved meal, G′ and G″ were not influenced by deformation in the amplitude sweep. Complex viscosities decreased with frequency (in all samples) and were independent of deformation (in extruded meal and bran). In shear experiments, β-glucan solutions were structurally viscous non-Newtonian solutions with rheostable behaviour. β-Glucan (2%) from bran had the highest and that from autoclaved meal had the lowest apparent and process viscosities. Fluid dynamic parameters may influence the flow, diffusion or transport behaviour of β-glucan during digestion processes in the small intestine, but the influence of the viscous behaviour is limited. [Copyright &y& Elsevier]

Abstract: Surface disposition of mine tailings in paste form is a new disposal technique, and to achieve a desired depositional geometry, it is necessary to characterize the paste''s flow properties. This study investigates how water content affects the flow behaviour and depositional geometry of tailings and kaolinite pastes, which are shear-thinning, high solids content, mineral pastes. A stress-controlled rheometer and a strain-controlled viscometer with vane fixtures were used to characterize the yield behaviour of the pastes, and three types of yield stress were determined. A flume apparatus was used to simulate paste deposition under laboratory conditions. The depositional angle, determined from the flume tests, and the yield stresses, determined from the rheometers, decreased as the water content increased. For each type of yield stress, a linear relationship was found between the depositional angle and the Sofra–Boger dimensionless group (τ y ′Fr/Re), with the linear coefficient depending on paste type. [Copyright &y& Elsevier]