Search

Abstract In the present work, a simple intelligence-based computation of artificial neural networks with the Levenberg-Marquardt backpropagation algorithm is developed to analyze the new ferromagnetic hybrid nanofluid flow model in the presence of a magnetic dipole within the context of flow over a stretching sheet. A combination of cobalt and iron (III) oxide (Co-Fe2O3) is strategically selected as ferromagnetic hybrid nanoparticles within the base fluid, water. The initial representation of the developed ferromagnetic hybrid nanofluid flow model, which is a system of highly nonlinear partial differential equations, is transformed into a system of nonlinear ordinary differential equations using appropriate similarity transformations. The reference data set of the possible outcomes is obtained from bvp4c for varying the parameters of the ferromagnetic hybrid nanofluid flow model. The estimated solutions of the proposed model are described during the testing, training, and validation phases of the backpropagated neural network. The performance evaluation and comparative study of the algorithm are carried out by regression analysis, error histograms, function fitting graphs, and mean squared error results. The findings of our study analyze the increasing effect of the ferrohydrodynamic interaction parameter $$\beta$$ β to enhance the temperature and velocity profiles, while increasing the thermal relaxation parameter $$\alpha$$ α decreases the temperature profile. The performance on MSE was shown for the temperature and velocity profiles of the developed model about 9.1703e−10, 7.1313ee−10, 3.1462e−10, and 4.8747e−10. The accuracy of the artificial neural networks with the Levenberg-Marquardt algorithm method is confirmed through various analyses and comparative results with the reference data. The purpose of this study is to enhance understanding of ferromagnetic hybrid nanofluid flow models using artificial neural networks with the Levenberg-Marquardt algorithm, offering precise analysis of key parameter effects on temperature and velocity profiles. Future studies will provide novel soft computing methods that leverage artificial neural networks to effectively solve problems in fluid mechanics and expand to engineering applications, improving their usefulness in tackling real-world problems.

Deep-sea hydraulic collection is a key technology for seabed mineral resource extraction, offering higher efficiency and environmental protection compared to other collection methods. However, due to their complex characteristics, the suction properties and influencing factors of polyhedral particles in hydraulic suction collection remain elusive. This study utilized dimensionless methods and conducted experiments to analyze the flow characteristics in cone-shaped collection hoods and the distribution of suction force on polyhedral particles, and researched the effect of various parameters, such as Φ, H/R, R/S, and H/dp (referring to the nomenclature given in the last part of this paper), on the suction force coefficients of polyhedral particles based on the suction force coefficients of spheres by acquiring the suction coefficient ratio (kc). The results indicate the following: (1) the presence of suction and coherent vortices in the horizontal positions of 0.1R to 0.2R within the central region, which move with changes in pump suction or cove height, benefiting particle collection; (2) the particle suction force (Fd) decreases with increasing sphericity (Φ), with a more pronounced decline in high-speed flow fields, exhibiting two peaks and one trough in the Fd curve within the hood's flow field; (3) the kc generally increases with decreasing Φ at the same collection position, showing increasingly stable fluctuations, and kc is sensitive to surrounding flow velocities with a rapid growth trend at higher speed, revealing that the suction coefficient (Cd) of polyhedral particles is significantly larger than that of spherical particles with increasing flow speed in high-speed flow fields; (4) Fd decreases with increasing H/dp, with a noticeable slowdown when H/dp exceeds 3.5. This study reveals the force characteristics and influencing factors of non-spherical coarse particles in hydraulic suction collection flow fields, providing insights for the development of collection technologies and equipment for deep-sea solid mineral resources, particularly irregular coarse particles. [ABSTRACT FROM AUTHOR]

This study aimed to explore the variability in nasal airflow patterns among different sexes and populations using computational fluid dynamics (CFD). We focused on evaluating the universality and applicability of dimensionless parameters R (bilateral nasal resistance) and ϕ (nasal flow asymmetry), initially established in a Caucasian Spanish cohort, across a broader spectrum of human populations to assess normal breathing function in healthy airways. In this retrospective study, CT scans from Cambodia (20 males, 20 females), Russia (20 males, 18 females), and Spain (19 males, 19 females) were analyzed. A standardized CFD workflow was implemented to calculate R‐ϕ parameters from these scans. Statistical analyses were conducted to assess and compare these parameters across different sexes and populations, emphasizing their distribution and variances. Our results indicated no significant sex‐based differences in the R parameter across the populations. However, moderate sexual dimorphism in the ϕ parameter was observed in the Cambodian group. Notably, no geographical differences were found in either R or ϕ parameters, suggesting consistent nasal airflow characteristics across the diverse human groups studied. The study also emphasized the importance of using dimensionless variables to effectively analyze the relationships between form and function in nasal airflow. The observed consistency of R‐ϕ parameters across various populations highlights their potential as reliable indicators in both medical practice and further CFD research, particularly in diverse human populations. Our findings suggest the potential applicability of dimensionless CFD parameters in analyzing nasal airflow, highlighting their utility across diverse demographic and geographic contexts. This research advances our understanding of nasal airflow dynamics and underscores the need for additional studies to validate these parameters in broader population cohorts. The approach of employing dimensionless parameters paves the way for future research that eliminates confounding size effects, enabling more accurate comparisons across different populations and sexes. The implications of this study are significant for the advancement of personalized medicine and the development of diagnostic tools that accommodate individual variations in nasal airflow. [ABSTRACT FROM AUTHOR]

In order to improve the propulsive performance of the existing pure heaving motion hydrofoil, the effect of varying stiffness ratio K *, damping ratio C * and inertia ratio J * on the propulsive efficiency of the semi-active NACA 0012 hydrofoil is systematically investigated by using the combination of CFD, Taguchi method and neural network. The results show that the passive pitching motion can significantly affect the propulsive performance of the hydrofoil. Compared to the pure heaving hydrofoil, the propulsive efficiency of the optimized semi-active hydrofoil can be improved by up to 20.97%. Further analysis reveals that the passive pitching motion can weaken the strength of the vortex around the hydrofoil, thus reducing the thrust and lift force on the hydrofoil, which results less power consumed by the active heaving motion of the hydrofoil. Although the thrust coefficient is reduced, the energy consumed by the passive pitching hydrofoil is reduced more, which leads a higher propulsive efficiency of the semi-active hydrofoil. [ABSTRACT FROM AUTHOR]

In multiphase particulate systems, the turbulence of the continuous phase (gas or liquid) is modulated due to interactions between the continuous phase and the suspended particles. Such phenomena are non-trivial in the essence that addition of a dispersed phase to a turbulent flow complicates the existing flow patterns depending on the physical properties of the particles leading to either augmentation or attenuation of continuous phase turbulence. In the present study, this aspect has been comprehensively analysed based on the available experimental data obtained from the well-studied turbulent flow systems such as channel and pipes, free jets and grids. Relevant non-dimensional parameters such as particle diameter to integral length scale ratio, Stokes number, particle volume fraction, particle momentum number, and particle Reynolds number have been utilised to characterise the reported turbulence modulation behavior. Some limitations of these commonly used dimensionless parameters to characterise turbulence modulation are discussed, and possible improvements are suggested. [ABSTRACT FROM AUTHOR]

In this study, a support vector machine (SVM) and three optimization algorithms are used to develop a discharge coefficient (Cd) prediction model for the semi-circular side weir (SCSW). After that, we derived the input and output parameters of the model by dimensionless analysis as the ratio of the flow depth at the weir crest point upstream to the diameter (h1/D), the ratio of main channel width to diameter (B/D), the ratio of side weir height to diameter (P/D), upstream of side weir Froude number (Fr), and Cd. The sensitivity coefficients for dimensionless parameters to Cd were calculated based on Sobol's method. The research shows that SVM and Genetic Algorithm (GA-SVM) have high prediction accuracy and generalization ability; the average error and maximum error were 0.08 and 2.47%, respectively, which were about 95.72 and 60.86% lower compared with the traditional empirical model. The first-order sensitivity coefficients S1 and global sensitivity coefficients Si of h1/D, B/D, P/D, and Fr were 0.35, 0.07, 0.13, and 0.02; 0.63, 0.25, 0.30, and 0.32, respectively. h1/D has a significant effect on Cd. In particular, when h1/D < 0.24 and 0.48 < Fr < 0.58, 0.67 < Fr < 0.72, the discharge capacity of the SCSW is relatively large. HIGHLIGHTS We developed an effective and high-accuracy model for predicting the Cd of SCSW.; The importance of dimensionless parameters on Cd was quantified by Sobol's method.; It explored the flow characteristics of semi-circular side weir.;

Deep-sea hydraulic collection is a key technology for seabed mineral resource extraction, offering higher efficiency and environmental protection compared to other collection methods. However, due to their complex characteristics, the suction properties and influencing factors of polyhedral particles in hydraulic suction collection remain elusive. This study utilized dimensionless methods and conducted experiments to analyze the flow characteristics in cone-shaped collection hoods and the distribution of suction force on polyhedral particles, and researched the effect of various parameters, such as Φ, H/R, R/S, and H/dp (referring to the nomenclature given in the last part of this paper), on the suction force coefficients of polyhedral particles based on the suction force coefficients of spheres by acquiring the suction coefficient ratio (kc). The results indicate the following: (1) the presence of suction and coherent vortices in the horizontal positions of 0.1R to 0.2R within the central region, which move with changes in pump suction or cove height, benefiting particle collection; (2) the particle suction force (Fd) decreases with increasing sphericity (Φ), with a more pronounced decline in high-speed flow fields, exhibiting two peaks and one trough in the Fd curve within the hood’s flow field; (3) the kc generally increases with decreasing Φ at the same collection position, showing increasingly stable fluctuations, and kc is sensitive to surrounding flow velocities with a rapid growth trend at higher speed, revealing that the suction coefficient (Cd) of polyhedral particles is significantly larger than that of spherical particles with increasing flow speed in high-speed flow fields; (4) Fd decreases with increasing H/dp, with a noticeable slowdown when H/dp exceeds 3.5. This study reveals the force characteristics and influencing factors of non-spherical coarse particles in hydraulic suction collection flow fields, providing insights for the development of collection technologies and equipment for deep-sea solid mineral resources, particularly irregular coarse particles.

A single-phase incompressible bicomponent transient oil mixing model was established based on the mechanism of flow, heat, and mass transfer of refined oils to obtain the flow field and concentration distribution of the component at the mixed segment during the batch transportation process. A new model for the axial diffusion coefficient was proposed, which included the turbulent diffusion coefficient and the coefficients derived from the differences in fluid physical properties. The new diffusion coefficient calculation formula presented in this paper could make the error very small when the calculated concentration distribution value of the mixing section is compared with the experimental value. Based on the many factors that affect the flow features during the oil replacement process in the mixed-oil section, the main dimensionless parameters (Reynolds, Peclet, Prandtl, Richardson, Schmidt) are selected by using the dimensional analysis method. The mixed segment had a high Pr and Pe. With an increasing concentration of lighter oil, the Pr decreased while the Pe and Re increased. The Ri was always less than 1, which implied that the buoyancy is not important, and the gravity effect can be ignored during the generation process of oil mixing according to the definition of Ri that buoyancy is dominant when it is greater than 1. The change of Sc versus the concentration of gasoline was small, and Sc was always close to 100, which indicated that the momentum diffusion was greater than the mass diffusion in the process of oil mixing. Sensitivity analysis was carried out based on the tailing amount and tailing length of the mixed section. It was concluded that the influence of pipe diameter, flow rate, temperature, and diffusion coefficient on the tailing amount and tailing length had the same trend. A single-phase incompressible two-component transient oil-mixing model is established to obtain the flow field and component concentration distribution in the mixing section during batch transportation in this paper. The flow characteristics and tailing phenomena of the mixed-oil section are determined by studying the dimensionless numbers (Reynolds, Peclet, Prandtl, Richardson, Schmidt) in the oil change process of the mixed-oil section. The experimental results could predict the distribution of oil mixture concentration under specific working conditions. The influences of the difference of oil physical properties, turbulence effect as well as the adsorption effect of the pipe wall on the distribution of oil mixture concentration have also been discussed. The research results show that this technology provides the location and concentration distribution of the mixed oil segment when it is applied to practical cases, which gives technical support for detecting and cutting the mixed oil segment during the process of batch transportation and also guides the accurate cutting of the mixing segment. [ABSTRACT FROM AUTHOR]

Dimensionless parameters and scaling laws that describe the geometric dimensions of a cermet weld bead formed during direct metal deposition are determined. A Ti64 titanium alloy and ceramics (silicon carbide, SiC) with different volume fractions are used as a powder mixture. A model for estimating the thermophysical parameters of a heterogeneous material is proposed. It is shown that, regardless of the volume fraction of ceramics, the dimensionless geometric parameters of a single track (depth, width, and height) depend on two dimensionless parameters: normalized enthalpy and the Peclet number. Also, these dependences can be approximated by algebraic expressions. [ABSTRACT FROM AUTHOR]

Auto-ignition, reaction front propagation, and detonation development are foundational events in combustion, and are relevant to the occurrence of engine knock. It is generally understood that different auto-ignition modes can be initiated by non-uniform initial temperatures, manifesting the transition from supersonic to subsonic combustion modes with increasing temperature gradients. In this work, we have investigated the auto-ignition and reaction front propagation of syngas/air mixtures initiated by wide-ranging temperature gradients, in both spherical and planar coordinates, and have identified a universal detonation response diagram with multiple, non-monotonic boundaries of auto-ignition modes under engine-relevant conditions. Specifically, it is shown that with increasing gradient steepness, in addition to the conventional three regimes of supersonic auto-ignition deflagration, detonation development, and subsonic auto-ignition deflagration, the reaction front propagation speed would first decrease dramatically and then increase, hence inducing additional detonation regimes. Consequently, two detonation peninsulas are identified, with the first corresponding to the well-established Bradley detonation peninsula and the second manifesting a broader detonation regime. Both detonation peninsulas depend on the hotspot size and they can connect together when the hotspot radius becomes sufficiently large. The transient auto-ignition processes and chemical-gas dynamic interactions agree with the typical characteristics of various auto-ignition modes. Finally, auto-ignition modes are summarized in the detonation diagram, in which the Bradley detonation peninsula is well reproduced and the new detonation peninsula is quantitatively determined. The present study demonstrates that auto-ignition modes are significantly affected by the non-monotonic behavior of reaction front propagation, and the use of actual propagation speed is necessary for steeper temperature gradients in order to determine more accurate dimensionless parameters. [ABSTRACT FROM AUTHOR]

Understanding the impact forces exerted by debris flows is limited by a lack of direct field measurements and validated numerical models. In this study, we use real‐time impact‐force measurements and field observations of debris flows recorded by a sensor network in Jiangjia Ravine, China, to quantify the impact‐force distribution of natural debris flows. We observed one debris flow event during and after a storm on 25 August 2004, including 42 short‐duration surges and seven long‐duration surges, and impact‐force signals were successfully recorded for 38 surges. Our observed debris flows comprise high‐viscosity laminar flows with high sediment concentration and frequent solid‐to‐solid interactions. We identified a large magnitude (up to 1 kN), high‐frequency (greater than 1 Hz) fluctuating component of the impact force that we interpret as solid particle impact on the sensors. The variability of particle impact forces increases with the mean impact force. Our results show that a log‐logistic distribution can describe the probability density distribution of impact forces. Solid‐dominated surges and fluid‐dominated intersurge flows have similar impact‐force distributions, but surges usually have heavy tails. We created a dimensionless number to describe the impact force and correlated it against existing dimensionless parameters. Finally, we develop a simple particle impact model to understand the relationship between flow dynamics and the impact force inside debris flows that could be applied to improve debris‐flow flume experiments and design debris‐flow hazard mitigation measures. Plain Language Summary: Debris flows are fast‐moving mixtures of dirt and water that can cause huge damage to buildings and infrastructures and harm people. For effective hazard protection, we need to understand the impact forces exerted by debris flows. In this study, we measured impact forces at the high temporal resolution of 49 debris‐flow surges during and after a storm on 25 August 2004, recorded by a sensor array in Jiangjia Ravine, southwestern China. We develop statistical descriptions of the mean and the variability of the force and derive a relationship between flow dynamics and the impact force using a simple particle impact model. Our results could be applied to improve the future design of debris‐flow hazard mitigation measures. Key Points: Log‐logistic distribution is a good fit for debris‐flow impact force probability density functionsDebris‐flow surges and intersurge flows have similar impact force distribution, but surges usually have heavy tailsA simple particle impact model can explain the debris‐flow impact force signal [ABSTRACT FROM AUTHOR]

An overview of laser welding methods and additive manufacturing technologies used in modern mechanical engineering is given, and the main trends and aspects of these technologies are discussed. Laser welding processes of thermally hardened aluminum alloys and problems of obtaining high-strength welded joints are considered. The additive growth of heterogeneous materials is analyzed taking into account the dimensionless parameters determining the structure of materials fabricated by additive manufacturing. [ABSTRACT FROM AUTHOR]

Enhancing the predictability of radon flux in fractured environments, particularly in confined spaces, is a crucial step towards mitigating the profound health risks associated with radon gas exposure. However, previous models on fluid transport through fractured rock have focused on the relationship between radon flux and aperture in fractures and faults. However, there is paucity of understanding on the influence of rock geo-mechanical properties on radon flux. In addition, there are limited methods of characterizing rocks in relation to radon flux. The numerical model presented in this study incorporated rock properties such as Young's modulus and Poisson ratio with rock aperture to develop a dimensionless radon flux for opening-mode fractures, and five dimensionless parameters (e.g., Geofluid number, Decay number, Fracgen number, Geofrac number, and Geopeclet number) were introduced to characterize fractures in terms of radon transport. Furthermore, these newly discovered relationships were used to conduct a series of flow simulations on fracture networks using the discrete fracture network model (DFN). This model establishes a quantitative framework for predicting radon flux through open-mode fractures and the influence of rock geo-mechanical properties. • Established relationship between rock geo-mechanical properties and radon flux. • Developed characterization mechanism for rocks such that these properties can be used to predict the potential exposure to radon. • Characterization method developed are dimensionless numbers that can be associated with rocks, concrete slabs and other radon bearing sources. [ABSTRACT FROM AUTHOR]

Combined structure of weir and gate due to the simultaneous flow of suspended material from on the overflow and material deposited in the flow of water from the valve section, provides better conditions compared to other structures used to measure the discharge in the channels. Nowadays, numerical solution methods without the need of laboratory equipment and the ability to calculate the desired parameters, with low time and cost is considered as one of the efficient methods of flow analysis. In this research, by using CFD and numerical solution method with FLOW-3D software for different diameters of combined structure of weir and gate was simulated. Flow simulation was performed in a channel with 3 mm length, 0.4 mm width and 0.5 mm height. The models were studied in cylindrical diameter of 5, 7.5, 10 and 12.5 cm, and for openings gates of 1, 2 and 3 cm. The flow was also simulated and studied for all models at 4 discharges of 12, 16, 20 and 22 lit/s. Comparing the discharge coefficient results with the dimensionless parameter of water depth upstream to water depth downstream of the overflow-valve combined model, it was observed that the numerical results obtained using the RNG turbulence model provide closer data to laboratory results. In the validation stage of numerical results with laboratory outputs of previous researches, the error percentage of the simulated model was calculated to be less than 5%, which indicates the acceptable accuracy of numerical modeling. The results showed that with increasing the flow, when the diameter and opening of the valve are fixed, the flow coefficient increases. At a constant diameter of the overflow-valve model, the flow coefficient decreases in exchange for increasing the valve opening. For a constant flow rate and diameter, changes in flow rate decrease with increasing valve opening height. It was also observed that the curvature of the flow surface profile increases with increasing diameter of the cylindrical model.

The operation of the centrifugal disk pump is experimentally studied. To summarize experimental data, dimensionless parameters are introduced. A method for calculating the flow rate, pressure, and throttling characteristics is proposed. The method ensures accuracy sufficient fort engineering calculations. [ABSTRACT FROM AUTHOR]

This manuscript discusses the positional systems used in intelligent robots. One of the characteristic problems that arise in such systems is associated with friction, including sticking during the process. Friction greatly affects the positioning accuracy of the actuators of controlled robots, especially if a pneumatic actuator is used as a motor. The work is devoted to the study and solution of this problem. Since it is impossible to completely eliminate the effect of friction, ways to minimize this effect are being investigated using a targeted choice of system parameters. For this purpose, the method of multicriteria optimization of a detailed mathematical model is applied on the example of a pneumatic positional system, as the most sensitive to friction. The paper considers the first stage of optimization associated with visualization and preliminary analysis of the process in order to prepare it for performing a system procedure. The dynamics equations of an intelligent positional system are written out, both in full-size and dimensionless one. The most convenient mathematical model of friction is presented terms of its use in the process of optimizing the entire control system. A procedure for visualizing the optimization process in the form of a graphical interface has been developed. The first stage of the intelligent drive system optimization procedure has been carried out. The paper presents at which parameters of the control system the "stick-slip" effect has less influence on the positioning process. [ABSTRACT FROM AUTHOR]

In the study, experimental and theoretical studies were carried out to assess the influence of the shapes of dents in the tank wall on the stress-strain state of the defect zone. By testing fragments of a cylindrical tank, it was found that the most appropriate expression is (5), which could take into account the leaching of the tank wall, resulting in a decrease in the stress concentration index. At the same time, during theoretical studies in this paper, it was found that polynomials determined the stress concentration coefficient, where the obtained analytical expression data were compared with the data determined numerically in the ANSYS program, and it was found that the spread was from 2% to 10%. According to the results of a numerical study of the stress-strain state of the dent zone in the tank wall, graphical dependences of the stress concentration coefficient on the dimensionless depth of the dent for various values of the dimensionless radius of the dents and do not exceed 2% of the indicators that are obtained. At the conclusion of the experimental and numerical studies, a conclusion was made about the degree of influence of the geometric dimensions of the dents on the stress concentration index. [ABSTRACT FROM AUTHOR]

To reveal the temperature rise evolution mechanism of isotropic media subjected to reciprocating motion constant-strength point heat source, various forms of analytical solutions are derived on the basis of differentiated relative scales, and non-dimensionalized parameters are designed to characterize the thermal distribution regularities by utilizing numerical calculations. Temperature rise curves of media subjected to a reciprocating motion point heat source allow similar quasi-steady-state characteristics to appear, which finally achieve a stable state, so that the values of surplus temperature oscillate around the constant time-average quantity. The time to reach quasi-steady state, the time-averaged quantity and the fluctuation amplitude of surplus temperature are comprehensively impacted by the dimensionless distance parameter γ, the convective heat transfer parameter ω and the velocity and travel parameter β. This work discusses influence rules of temperature evolution in various relative-scale media and further enriches the moving heat source theory. [ABSTRACT FROM AUTHOR]

Traditionally, empirical correlations for predicting respiratory tract deposition of inhaled aerosols have been developed using limited available in vivo data. More recently, advances in medical image segmentation and additive manufacturing processes have allowed researchers to conduct extensive in vitro deposition experiments in realistic replicas of the upper and central branching airways. This work has led to a collection of empirical equations for predicting regional aerosol deposition, especially in the upper, nasal and oral airways. The present section reviews empirical correlations based on both in vivo and in vitro data, which may be used to predict total and regional deposition. Equations are presented for predicting total respiratory deposition fraction, mouth-throat fraction, nasal, and nose-throat fractions for a large variety of aerosol sizes, subject age groups, and breathing maneuvers. Use of these correlations to estimate total lung deposition is also described. [ABSTRACT FROM AUTHOR]

The free convection flow of Prabhakar fractional Jeffrey fluid on an oscillated vertical plate with homogenous heat flux is investigated. With the help of the Laplace transform and the Boussinesq's approximation, precise solutions for dimensionless momentum may be found. The temperature and velocity of Prabhakar fractional time free convection flows are compared to conventional thermal transport, as shown by Fourier's law. They met all of the requirements and recovered Newtonian and ordinary Jeffrey fluid solutions from fractional Jeffrey fluid. Finally, graphs show the effect of various physical parameters such as fractional parameters, Grashof number, Prandtl number and Jeffrey parameters on both temperature and velocity.

Results of a series of experiments aimed at studying laser cladding of individual tracks with the use of the B4C–Ti–6Al–4V cermet powder mixture are reported. The influence of laser cladding parameters (radiation power, beam motion velocity, and focus position) on the characteristics of tracks being formed (geometric sizes, microhardness, and elemental composition) is studied. It is shown that an increase in the concentration of reinforcing particles in the initial powder mixture alters the character of mass transfer inside the melt pool, leading to changes in the shape of the single track. It is found that a complex heterogeneous structure is formed in the melt pool, including secondary phase compounds formed in chemical reactions due to in-situ synthesis. The microhardness values at various points of the single track are observed to differ by more than a factor of 2 (in the interval HV0.3 = 548–1415). [ABSTRACT FROM AUTHOR]

Estimation of withdrawal water and filtered sediment amounts are important to obtain maximum efficiency from an intake structure. The purpose of this study is to develop empirical equations to predict Water Capturing Performance (WCP) and Sediment Release Efficiency (SRE) for Coanda type intakes. These equations were developed using 216 sets of experimental data. Intakes were tested under six different slopes, six screens, and three water discharges. In SRE experiments, sediment concentration was kept constant. Dimensionless parameters were first developed and then subjected to multicollinearity analysis. Then, nonlinear equations were proposed whose exponents and coefficients were obtained using the Genetic Algorithm method. The equations were calibrated and validated with 70 and 30% of the data, respectively. The validation results revealed that the empirical equations produced low MAE and RMSE and high R2 values for both the WCP and the SRE. Results showed outperformance of the empirical equations against those of MNLR. Sensitivity analysis carried out by the ANNs revealed that the geometric parameters of the intake were comparably more sensitive than the flow characteristics. [ABSTRACT FROM AUTHOR]

Productivity in laser powder bed fusion systems can be increased by using high layer thickness (>40 μm). The process parameters for high layer thickness are typically found by one-factor-at-a-time, design of experiments, or computationally intensive numerical simulations. In this paper, a method to scale-up the process parameters from low to high layer thickness is proposed. The method is based on dimensionless parameters from the analytical model. Through the proposed scale-up method, the build rate increase was proportional to an increase in layer thickness. The scale-up method was demonstrated for laser powder bed fusion of stainless steel 316L from 30 to 50 μm layer thickness and from 50 to 70 μm layer thickness. For both cases, no detriment to part density was observed—measured densities before and after the scale-up were above 99.6%. The density results obtained were within high density windows with variation of parameters resulting in the same respective volumetric energy densities and one-factor-at-a-time parameter studies. There was no significant change in tensile properties after the scale-up except reduction in elongation at break in the XY direction. The comparable mechanical properties before and after the scale-up method were attributed to the observed similarities in microstructure features such as the crystal orientation, cell sizes, and proportions of low and high angle grain boundaries. [ABSTRACT FROM AUTHOR]

Unconventional reservoirs are normally characterized by dual porous media, which has both multi-scale pore and fracture structures, such as low permeability or tight oil reservoirs. The seepage characteristics of such reservoirs is mainly determined by micro-fractures, but conventional laboratory experimental methods are difficult to measure it, which is attribute to the dynamic cracking of these micro-fractures. The emerging digital core technology in recent years can solve this problem by developing an accurate pore network model and a rational simulation approach. In this study, a novel pore-fracture dual network model was established based on percolation theory. Fluid flow in the pore of two scales, micro-fracture and matrix pore, were considered, also with the impact of micro-fracture opening and closing during flow. Some seepage characteristic parameters, such as fluid saturations, capillary pressure, relative permeabilities, displacement efficiency in different flow stage, can be predicted by proposed calculating method. Through these work, seepage characteristics of dual porous media can be achieved.

The current paper highlights the contribution of the Dowson and Higginson work to numerical line contact elastohydrodynamic lubrication film thickness prediction and the Hamrock and Dowson contribution to the film thickness prediction in elliptical contacts. This paper shows that, even by today's standards, both the numerical pressure and film thickness results and the curve-fitted film thickness predictions are very accurate. As for the elliptical results, the authors show that the original predictions remain surprisingly accurate for moderately elliptical contact. For very long elliptical contacts, their prediction does not tend to a line contact asymptote. This paper then concludes that the predicted pressure spikes by Dowson, Higginson, and Hamrock are correct in shape and amplitude, at least near pure rolling conditions. [ABSTRACT FROM AUTHOR]

The dynamic interaction between lining and soil in an underground structure is an important basic problem of soil dynamics. The transient dynamic response of a cylindrical cavity with lining embedded in unsaturated soil is studied. Based on the potential function and Laplace transform method, the expression of potential function in the transformation domain is derived, and the general solutions of stress and displacement are obtained. Combining the boundary conditions and the continuous conditions on the interface between lining and soil, the exact analytical solutions are determined. By the degradation of unsaturated soil to saturate status, the solutions for saturated soil are also presented and the rationality of the solution is verified. Based on the analytical solutions, a large number of parameter analyses are conducted. The results show that the maximum radial displacement and the maximum circumferential stress appear on the inner surface of the lining and at the interface, respectively. In the unsaturated clay soil, the dynamic responses of lining disappear in a shorter time. Both the shear modulus and the thickness of the lining have significantly effects on the dynamic response peak value of the structure. Increasing the shear modulus or thickness can effectively reduce the peak value of the radial displacement in the lining. The influence range of circumferential stress and pore fluid pressure in unsaturated soil is not more than 22.5 times of the hole diameter distance. [ABSTRACT FROM AUTHOR]

This work presents a physics-based predictive model for temperature rise in cylindrical solids heated by constant-strength, periodic-motion heat source. The heat source motion path, heat transfer boundary conditions and solid dimension are considered in the theoretical model. Analytical solutions to both the infinite or finite length cylinders are constructed with respect to convection and corresponding boundary conditions. Dimensionless controlling parameters are discussed to reveal temperature field evolution. The predicted results in the temperature rise agreed well with the measured data for a Z-direction feeding drive screw shaft system. The proposed model provides an efficient and accurate design tool for engineering calculation and process-parameter planning through inverse analysis.

Concentrated Solar Power (CSP) technology stands out among other renewable energy sources not only because of its ability to address current energy security and environmental challenges but because its energy can be stored for future use. To ensure optimum performance in this system, the heat losses need to be evaluated for better design. This work studies the natural convection in the receiver absorber tube of a CSP plant taking into consideration the influence of neighboring absorbers. A 2-Dimensional model was adopted in this study. Initially, a single absorber tube was considered, it was subjected to heat flux at the top wall, the bottom wall was insulated and a temperature differential was set up at the lateral walls. The dimensionless forms of Navier-Stokes and energy equations were solved using the finite element formulation of COMSOL Multiphysics software. The result obtained for a single absorber tube showed good agreement with existing research works. This validated model was then extended to multiple absorber tubes (two to six absorber tubes). On the basis of the study, there is an observed increase in the intensity and dominance of convective heat transfer with an increase in the number of absorber tubes. This is occasioned by an increase in the average surface temperature as well as average Nusselt number. For the Rayleigh number of 104, 105 and 106, the average Nusselt number increases with the number of absorber tubes by 13.87 %, 6.26 %, and 1.55 %, respectively. This increment suggests effect of thermal interactions among the neighboring absorber tubes. [ABSTRACT FROM AUTHOR]

In this study, the tensile strength, impact strength, and the hardness of the weld are determined. A criterion is proposed for describing the effect of residual stress on the weld mechanical properties. Dimensionless parameters such as Rya (the average of residual stress over the material yield strength), Rym (the maximum residual stress over the material yield strength), Ru2 (the difference in the residual stress over the material ultimate strength), and Ru3 (the difference ratio between the maximum and minimum of three-dimensional residual stresses over the material ultimate strength) are presented to describe the influence of residual stresses on the actual mechanical behavior of the welded pipe. Maximum Rya criterion and lowest strength are obtained at the weld gap center on the external surface of the pipe. The sharp decline in Ru2 criteria is consistent with the severe reduction in impact strength perpendicular to the weld gap.

Among the factors limiting the use of sliding seal actuators in robotic positioning systems, the main ones are two the compressibility of the working fluid (air or liquid) and friction. This article discusses the problem of choosing a friction model for solving problems of controlling positional systems, primarily with a pneumatic drive based on a digital twin – a detailed mathematical model. Friction is usually described as the process of mechanical interaction of touching bodies at their relative displacement in the plane of contact (external friction), or at the relative displacement of parallel layers of a liquid, gas, or deformable solid (internal friction, or viscosity). In most cases, friction is a useful phenomenon, making many common things possible, such as walking and braking on a car. On the other hand, friction can also cause undesirable consequences. For example, for high-precision mechanical systems, friction can degrade the overall performance of the system. The influence of friction is manifested by undesirable effects in the form of limit cycles, deviations in movement from a given trajectory, a decrease in positioning accuracy, etc. As one of the models a rather complex dynamic model of friction – the LuGre model was analyzed, which is widely used in many works. However, the authors stopped in this case with the simpler Karnopp model, which has the advantage of describing the interaction with the friction forces in the processes of transition from a state of rest to motion and vice versa. A general approach to the study of the dynamics and accuracy of the positional system is proposed, based on the use of a rationalized dimensionless mathematical model of the drive. Several numerical experiments were carried out on the obtained model, considering friction forces. Numerical experiments are shown in graphs. [ABSTRACT FROM AUTHOR]

In this paper, the processes occurring during laser-shock-wave processing of titanium alloys with the shape memory effect by the methods of dimensional analysis and finite element modeling are discussed. The main dimensionless parameters that control the distribution of residual stresses and the depth of the plastic zone arising during laser-shock-wave treatment were established to be the dimensionless duration of the action of the laser pulse and the peak pressure in the shock wave. The effect of the indicated dimensionless parameters on the residual stresses arising during laser-shock-wave processing in alloys with the shape memory effect was numerically studied based on the adopted constitutive relation, which takes into account the martensitic transformation. Numerical results that quantitatively reveal the regularities of the effect of the above dimensionless parameters on the residual stresses are obtained. Obtained by numerical modeling, the relation between the plastic zone depth and the peak pressure in the shock wave is confirmed by comparison with similar experimental results known in the literature. [ABSTRACT FROM AUTHOR]

To reveal the temperature rise evolution mechanism of isotropic media subjected to reciprocating motion constant-strength point heat source, various forms of analytical solutions are derived on the basis of differentiated relative scales, and non-dimensionalized parameters are designed to characterize the thermal distribution regularities by utilizing numerical calculations. Temperature rise curves of media subjected to a reciprocating motion point heat source allow similar quasi-steady-state characteristics to appear, which finally achieve a stable state, so that the values of surplus temperature oscillate around the constant time-average quantity. The time to reach quasi-steady state, the time-averaged quantity and the fluctuation amplitude of surplus temperature are comprehensively impacted by the dimensionless distance parameter γ, the convective heat transfer parameter ω and the velocity and travel parameter β. This work discusses influence rules of temperature evolution in various relative-scale media and further enriches the moving heat source theory.

In order to understand the behavior of the low-temperature water gas shift (WGS) reaction membrane reactor system and obtain better performance of the reactor, numerical simulations are performed with a two-dimensional axisymmetric model. Dimensionless analysis is applied to the governing equations, and then a set of dimensionless parameters are established. The effect of the parameters of Damkohler number (D a) and membrane permeability (P p) over a wide range on the performance of CO conversion and hydrogen recovery is studied, and the discussion of reaction phenomenon is presented. The WGS reaction is simulated under the operating conditions of 2 atm and two temperatures of 200 and 300 °C. The simulation results suggest that D a = 10 − 4 and P p = 10 − 1 are the optimum operating conditions for the reactor system where the conversion reaches nearly 100% exceeding the thermodynamic equilibrium conversion by 11% at 300 °C and the optimal hydrogen recovery is achieved simultaneously. The distribution of components along the axis of the reactor is checked, and then two crucial indicators are raised to assess the extent of reaction and hydrogen separation respectively, for the purpose of guidance for the length design of the reactor. Finally, the analysis of the effect of sweep gas on reactor performance suggests that the optimum flow rate of sweep gas is 0.2–0.5 L/min, and further enhancement of performance can be achieved by using counter-current sweep gas configuration. • A 2D symmetric model of WGSR membrane reactor is built. • Effect of dimensionless parameters and temperature is analyzed. • Effect of sweep gas flow rates and sweep gas modes is investigated. • Two indicators are proposed to guide the design of reactor geometric length. [ABSTRACT FROM AUTHOR]

This paper presents a study of cross-sectional parameters and optimal drag reduction performance specifically for drag reduction in rotating microgroove applications. Rotating triangular microgrooves with nine asymmetrical and symmetrical cross-sections were numerically studied. In addition, a representative symmetrical rotating microgroove was experimentally tested. Positive asymmetrical microgrooves (including symmetrical microgrooves) were found to be sensitive to rotating Reynolds numbers and produced more significant drag reduction. Compared with a dimensioned asymmetry variable and other dimensionless parameters, the dimensionless asymmetry variable i + could be used to describe drag reduction performance, which captured both the influence of microgroove cross-sectional asymmetry and turbulence intensity. A maximum drag reduction of up to 8.9% was obtained at 9.2 i +. With the exception of the torque, the velocity shift obtained from dimensionless velocity profiles could also be used to predict drag reduction performance, which has the potential for wider and more comprehensive application for any drag reduction technology. [ABSTRACT FROM AUTHOR]

This research investigates the effect of stress concentration factors (SCFs) in KT-connections retrofitted with concrete under axial loadings. 972 finite element models of KT-connections with various types of concrete and geometrical parameters have been modeled and analyzed using ANSYS APDL. SOLID 186 was used to mesh all parts of the model and to design the weld profile AWS recommendations were followed. The interaction between concrete and the chord was defined using ANSYS contact capability. Available experimental data was utilized to validate those models. Afterwards, the validated models were used to study the SCFs in different kinds of KT-connections filled with concrete. The results indicate a reduction of the maximum SCFs by around 50%–60% at the saddle points, and 17%–43% at the crown points compared to empty KT-joints. The reduction effect increases significantly when the concrete nominal compressive strength grades from C2, C40, and C50. In addition, in all types of loading conditions at the saddle points, the SCFs values increase. Among the nondimensional parameters, θ significantly affects SCFs crown points at the outer braces and saddle points at the central brace. Despite the clearly identified advantage of using concrete filling to reduce SCFs in the KT-joints, there are no studies or equations on these joints filled with concrete. Therefore, to calculate SCFs in KT-connections filled with concrete, some new formulae are developed and validated against the UK DoE acceptance standard. [Display omitted] • Stress concentration factors were investigated for concrete-filled tubular KT joints under axial loadings. • Effects of dimensionless geometric parameters and concrete grads were investigated thorough FE analysis. • The FE modeling was validated using experimental data on tubular joints. • Parametric equations were proposed to calculate maximum SCF in concrete-filled tubular KT joints. [ABSTRACT FROM AUTHOR]

The purpose of this study is to obtain better physical understandings of the theoretical thresholds of the insonation acoustic pressure amplitudes for medical diagnostic ultrasound applications. For this purpose, a physical model in terms of non-linear resonance of single bubble volumetric oscillations has been developed, to reproduce the threshold insonation acoustic pressure amplitudes that are numerical solutions of Gilmore's equation. It is confirmed, under the condition of the adiabatic state change of the in-bubble gas with a maximum temperature of 5000 K, the present model well-reproduces the influences of the insonation center frequency, the liquid viscosity and surface tension in a range of 0.5 to 16 MHz, 0.0 to 8.0 mPa･s, and 30 to 70 mN/s, respectively, on the threshold insonation acoustic pressure amplitudes. Based on this model, a dimensionless physical index of the insonation acoustic pressure amplitude with a threshold value and a set of fundamental dimensionless parameters constituting that index are defined.

Fuel atomization will seriously affect the combustion and emission characteristics of IC engine. It is important to study the atomization characteristics of single droplet under dynamic inertial force for improving the high precision secondary atomization model in cylinder. Firstly, the process of droplet atomization under sinusoidal inertial force was studied experimentally. Then, the effects of dimensionless parameters, including Bond number (Bo), gas-liquid density ratio (ρ G/L), gas-liquid viscous ratio (μ G/L), Weber number (We) and Reynolds number (Re), on the average wavelength and atomization time of droplet surface wave were numerically investigated. The results show that with the development of time, the droplet surface appears zonal standing wave, radial standing wave and volcanic standing wave in turn. When the droplet atomizes, the sub droplet sprays first from the top of the droplet, and the atomization intensity at the top is stronger than that at both sides. Bo , ρ G/L and Re have little influence on the average wavelength of droplet surface wave, μ G/L has no effect, while We has a great influence. As Bo , We and Re increase, the atomization time decreases rapidly at first, and then converges. When We > 104 or Re > 104, the effect of surface tension and viscous force on atomization time can be neglected. As ρ G/L increases, the atomization time first remains unchanged and then increases rapidly. When ρ G/L < 0.1, its influence can be neglected. μ G/L has no effect on the atomization time. Furthermore, according to the variation of the average wavelength and We number, the dimensionless form of the empirical formula for the average diameter of droplets is obtained: d m ∗ = (1.0 ± 0.1) ∙ We - 1 / 3 . Finally, the critical conditions of droplet atomization are determined based on the actual atomization time of IC engine. [ABSTRACT FROM AUTHOR]

• Possibility of integrating thermoelectric with gasifier cycle is investigated. • Different locations for adding TEG in a biomass power generation is investigated. • Adding thermoelectric to the condenser section increases efficiency from 16.76% to 17.93%. • Economic evaluation indicated the conditions under which the system is profitable. Thermoelectric waste heat recovery systems (WHRSs) can be used appropriately to recover wasted heat from various industrial processes. In the current work, new thermodynamic modeling was developed to harvesting waste heat from an integrated system includes an externally fired gas turbine and a biomass gasifier by three thermoelectric WHRSs. The biomass system consisted a gas turbine cycle, an organic Rankine cycle (ORC) and a domestic water heater were first thermodynamically modeled, and then effects of adding thermoelectric WHRSs to different locations of the system were investigated. It is observed that first law efficiency of the system (η 1) will become 17.11% (an increase of 0.35%) if the total output heat from the stack enters W H R S s. The efficiencies of the system can be increased from 16.76% to 17.93% by placing a WHRS on the condenser of ORC. Moreover, the operating parameters have a significant effect on the integrated system efficiency; the influence of increasing α G E on the efficiencies is in contrast to the effect of enhancing α c o n d . In addition, an economic assessment of integrating WHRSs with the biomass gasifier integrated system is conducted and the conditions are indicated under which the proposed system is profitable. Furthermore, the results of genetic algorithm based multi-objective optimization shows that with the use of γ DU = 2 and γ L , O R C = 30 defined thermal efficiencies are at their optimum state. [ABSTRACT FROM AUTHOR]

The influence of the laser beam parameters (power, motion velocity, and focus position) on the characteristics of the track being formed (size, elemental composition, and microhardness) is studied. If the difference in the laser radiation absorption coefficients in the heat conduction and keyhole regimes is taken into account, then the track sizes can be determined by a unified dependence on the energy parameter. The effect of the laser beam on the chemical composition and microhardness of cermet (WC-NiCrBSi) tracks is studied. Regardless of the track formation regime, these parameters are determined by a dimensionless parameter, which describes the degree of dilution of chemical substances. It is found that a track with the maximum mass fraction of tungsten and the greatest value of microhardness is formed at small values of the dimensionless parameter, which corresponds to the heat conduction regime. The microhardness of the deposited cermet structure is observed to be 4–5 times higher than the microhardness of the substrate material. [ABSTRACT FROM AUTHOR]