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This study focuses on the analysis of peristaltic transport of a hybrid nanofluid comprising deionized water as a base fluid and the multi-walled carbon nanotubes (MWCNTs) and copper oxide (CuO) as nanoparticles within a sinusoidal wavy porous duct, taking into consideration the influence of heat generation or absorption. The inaugural literature piece addresses the utilization of hybrid nanofluid in the context of peristaltic flow within ducts. To simplify the analysis, we have converted the non-dimensional equations into a two-dimensional (2D) coordinate system using the assumptions of a very long wavelength (δ < 1) and low Reynolds number (Re). The non-dimensional equations governing the behavior of the hybrid nanofluid are then solved numerically using the finite volume method. Numerical solutions for temperature and the 2D peristaltic flow are obtained with the assistance of the Mathematics software MATLAB. These solutions are subsequently represented graphically using MATLAB software. The graphical results highlight several key findings for important parameters. First, it is observed that the pressure rise, temperature profile, and pressure gradient in the hybrid nanofluid (CuMWCNTs/H2O) flow increases as heat generation increases. Furthermore, an increase in the nanoparticle volume fraction of both nanoparticles leads to a decrease in the pressure rise and pressure gradient in the hybrid nanofluid flow. Additionally, the widening of the channel reduces the pressure gradient and pressure rise in the CuMWCNTs/H2O hybrid nanofluid. The analysis also includes the visualization of streamlines for peristaltic transport. These streamlines reveal that an increase in amplitude results in larger bolus sizes, while heightened heat generation has the opposite effect, decreasing bolus sizes. The results of this investigation can be found in various cooling devices as flows in the ducts are very frequently utilized for the cooling process of engines. A further topic is common in applications related to microfluidics, heat exchangers, and biomedical devices where peristaltic pumping is employed. Our results are in 100% agreement with the existing literature in special cases. [ABSTRACT FROM AUTHOR]

Magnetic flux leakage (MFL) signal prediction is important in ferromagnetic defect evaluation and reconstruction. At present, the magnetic dipole model (MDM) is the most widely applied method because of its high efficiency. However, it has low accuracy when applied to analysing complex defects (complex in profile and magnetic permeability) due to the original setting of uniform magnetic charge distribution. To solve the issue, this paper proposes an improved MDM method for MFL inspection of ferromagnetic materials by calculating the non-uniform magnetic charge distribution. It partly applies the finite volume method (FVM) to derive the magnetic charge distribution on the defect surface, which makes it able to take into account the defect's profile and magnetic permeability distribution. The new magnetic charge distribution can increase the MDM's accuracy for complex defect MFL field prediction with little extra cost. Experimental results show that, when compared with traditional MDM, the proposed one can achieve a maximum 69% decrease in root mean squared error when analysing complex defects. Compared with the numerical method, the computation time could reach a great reduction. [ABSTRACT FROM AUTHOR]

In this work, we develop a new framework to deal numerically with discontinuous solutions in nonconservative hyperbolic systems. First an extension of the MOOD methodology to nonconservative systems based on Taylor expansions is presented. This extension combined with an in‐cell discontinuous reconstruction operator are the key points to develop a new family of high‐order methods that are able to capture exactly isolated shocks. Several test cases are proposed to validate these methods for the Modified Shallow Water equations and the Two‐Layer Shallow Water system. [ABSTRACT FROM AUTHOR]

Flow over an Iranian bridge deck is studied under an actual extreme flood event happening similarly nowadays in many countries due to climate change. Rigorous transient fluid-structure interaction analyses using the realizable k-ε turbulence model and the VOF Method are conducted. Geotechnical and abutments damages are neglected. Water surface profiles, velocity vectors, and hydrodynamic coefficients are determined. Based on the latest hydrological regime, particularly in supercritical flows, the results are partially compared against the latest advanced design codes, to evaluate the performance of their hydrodynamic and hydraulic provisions in similar incidents. It was acknowledged that the flood loads recommended by the Federal Highway Administration (FHWA) are fairly acceptable, Eurocode-1 predicts them rather accurately but not in extreme cases, and the Australian Standard (AS-5100.2) is less effective due to over-estimation of the hydrodynamic loads. Instead, the latter offers comprehensive user-defined hydraulic conditions. Furthermore, upon gradual rise of the water level to thrice the deck height, bridge stability is found to be at risk due to highly turbulent states. It is recommended that due to such threats, re-evaluation of flood regime, as well as its distinct hydrodynamic properties have to be accounted for, when evaluating existing bridges or designing new ones. [ABSTRACT FROM AUTHOR]

A numerical model is presented for solving the dam–reservoir interaction (DRI) problem in the time domain. The primary aim of this paper is to introduce a coupling method that could be simply implemented in a monolithic DRI model, yields a symmetrical system of equations, and maintains accuracy comparable to existing studies. The finite element method is employed to solve the equation of motion for the structure, and the finite volume method is for the Navier–Stokes equations in the fluid domain. These two solvers are coupled using an innovative approach to generate a pressure-based symmetric system of equations, which is resolved implicitly. Moreover, unlike most previous DRI studies, free surface waves are considered in the modeling procedure, and their effects are investigated. Comparison of the results with benchmark test cases from the literature demonstrates that the proposed numerical method is both straightforward and precise. [ABSTRACT FROM AUTHOR]

The air-sea UAV is made to be able to fly, change from land to water, and navigate through submerged water. However, as it moves from the air to the water, it experiences a significant impact force. The UAV's structure and components run the risk of being harmed by this strong impact force. The accelerations and forces involved in the transition process must therefore be understood through quantitative research. The method was created using computational fluid dynamics (CFD), which can manage the process of water entry. The simulation and calculations were carried out using the Fluent software suite from ANSYS Inc. The research examined the UAV's wing and center bodies independently and separately. 3-D models were used for the analyses of the center body, while 2-D models were used for the wing-body analyses. The transition flow and submerged methods were taken into consideration in obtaining the impact load that a body experiences when transitioning into water. Because it was substantiated using experimental results from prior studies, the transient-time analysis-based transition technique was shown to be reliable. The steady-state analysis of the submerged flow method can be used to quickly comprehend the pressure and velocity distribution over a body immersed in or entering the water. However, because it fails to account for the water's initial acceleration upon entry, the steady-state simulation underestimates the drag force. The submerged flow method's findings indicate that a sharp nose centre body diminishes drag more successfully. The transition method evaluations for the UAV slender body reveal controllable drag and impact forces. Furthermore, the study demonstrates that wedge-shaped leading edges for the wing-body reduce impact but may not be optimal when considering airlift. As a result, this research provides useful data for air-sea UAV structural design and movement conditions. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the effect of different beam distance by understanding laser beam influence on solder joint quality. The utilisation numerical-based simulations and experimental validation will help to minimise the formation of micro void in PTH that can lead to cracks and defects on passive devices. Design/methodology/approach: The research uses a combination approach of numerical-based simulation using Finite Volume Method (FVM) and experimental validation to explore the impact of different laser beam distances on solder joint quality in PTH assemblies. The study visualises solder flow and identifies the optimal beam distance for placing a soldering workpiece and a suitable tolerance distance for inserting the solder wire. Findings: The simulation results show the formation of micro void that occurs in PTH region with low volume fraction and unbalance heat concentration profile observed. The experimental results indicate that the focus point of the laser beam at a 99.0 mm distance yields the smallest beam size. Simulation visualisation demonstrates that the laser beam's converging area at +4.6 mm from the focus point which provides optimal tolerance distances for placing the solder wire. The high-power laser diode exhibits maximum tolerance distance at 103.6 mm from the focus point where suitable beam distance for positioning of the soldering workpiece with 50% laser power. The simulation results align with the IPC-A-610 standard, ensuring optimal filling height, fillet shape with a 90° contact angle and defect-free. Practical implications: This research provides implications for the industry by demonstrating the capability of the simulation approach to produce high-quality solder joints. The parameters, such as beam distance and power levels, offer practical guidelines for improving laser soldering processes in the manufacturing industry. Originality/value: This study contributes to the field by combining high-power laser diode technology with numerical-based simulations to optimise the beam distance parameters for minimising micro void formation in the PTH region. [ABSTRACT FROM AUTHOR]

Depleted low-permeability gas reservoirs are the primary storage media for underground hydrogen storage (UHS). An accurate assessment of the geomechanics and complex flow mechanisms in a depleted low-permeability gas reservoir is crucial for predicting the injection and production capabilities of UHS facilities. This paper proposes a novel hydromechanical multicomponent model that couples non-Darcy flow, relative permeability hysteresis (RPH), and geomechanics to evaluate the hydrogen storage capacity of UHS facilities in a depleted low-permeability gas reservoir. The coupled model was solved using a fully coupled strategy, employing the finite volume method to solve non-Darcy flow equations and the virtual element method to solve geomechanical problems. The results indicate that the high-velocity non-Darcy (hvnD) and geomechanical effects reduce the working gas volume by 12.82% and 10.56%, respectively. Additionally, the low-velocity non-Darcy (lvnD) effect causes the third stress/strain distribution to exhibit a "focusing" phenomenon, resulting in a 13.19% reduction in the working gas volume. This paper also describes a case where residual gas is captured by mechanisms such as "water lock" and "capillary capture" through the RPH effect. Considering the RPH effect, the gas-water transition zone expanded by 30%, and the peak volume of gas-containing pores in the water zone increased by 1.48 times. Ignoring the RPH effect led to a 19.73% overestimation of the utilization rate of the gas-containing pore space. Hence, this study achieves safe and successful seasonal hydrogen storage and provides theoretical support for designing multicycle operational plans. • A novel coupled hydro-mechanical multicomponent model was proposed. • Non-Darcy flow, hysteresis and geomechanical effects were evaluated thoroughly. • The underground hydrogen storage capacity could be evaluated accurately. [ABSTRACT FROM AUTHOR]

To analyze the noise induced by moving rigid structures in low Mach number flows, acoustic governing equations based on the viscous/acoustic splitting method and the arbitrary Lagrangian–Eulerian method are rigorously derived. In order to resolve the numerical instability generated in a non-uniform mean flow, the modified viscous/acoustic method, based on the filtering method, is developed. The acoustic equations are transformed into the same form as the incompressible flow equations by introducing the acoustic co-velocity and solved based on a collocated grid finite volume method. An approach for solving acoustic equation based on the PIMPLE algorithm is presented and computed in open-source computational fluid dynamics software OpenFOAM, which brings down communication costs and speeds up computing efficiency. Furthermore, the source term decomposition is extended to study the noise generated by each source term in a motion grid. Several examples including stationary and moving meshes have been designed to prove the accuracy of this approach. Finally, the aerodynamic and acoustic properties for the flow past a transversely oscillating cylinder at Re = 200, Ma = 0.2 in lock-in and non-lock-in regions is present. [ABSTRACT FROM AUTHOR]

In subsurface energy extraction, permeability or conductivity is the vital parameter for quantifying fluid flow in porous media. Three-dimensional digital core technique is widely used to calculate flow parameters and to analyze the internal structure and properties of rocks. However, one major problem is its high computational cost associated with fine-scale simulation of porous media, especially for large and complex rock samples. In this study, we propose to use subvolume properties to increase computational efficiency. Specifically, we first construct digital cores of dune sand and sandstone by CT scanning technology, and divide the whole core into multiple subvolumes and calculate their permeabilities. Then, we reassemble the subvolumes and compute the permeability for the whole core. This approach may lead to underestimation as the connectivity between subvolumes could be lost. To address this issue, we divide the whole core into different-sized subvolumes, and then use curve fitting to deduce the permeability of whole rock sample via extrapolation. The results show that the proposed method has improved accuracy, and is significantly faster than simulating the whole digital core, since the computation on subvolumes can be easily parallelized. This approach provides new ideas for accurate and efficient permeability estimation for digital porous media. [ABSTRACT FROM AUTHOR]

A three-dimensional model of polydisperse reactive sedimentation is developed by means of a multilayer shallow water approach. The model consists of a variety of solid particles of different sizes and densities, and substrates diluted in water, which produce biochemical reactions while the sedimentation process occurs. Based on the Masliyah–Lockett–Bassoon settling velocity, compressibility of the sediment and viscosity of the mixture, the system of governing equations is composed by non-homogeneous transport equations, coupled to a momentum equation describing the mass-average velocity. Besides, the free-surface depicted by the total height of the fluid column is incorporated and fully determined through the multilayer approach. A finite volume numerical scheme on Cartesian grids is proposed to approximate the model equations. Numerical simulations of the denitrification process exemplify the performance of the numerical scheme and model under different scenarios and bottom topographies. • Polydisperse reactive sedimentation. • Multilayer shallow water approach. • Denitrification and eutrophication processes. [ABSTRACT FROM AUTHOR]

A method for the evaluation of time-resolved entropy production in isothermal and incompressible flow is presented. It is applied as a postprocessing of the three-dimensional (3D) flow field obtained by time-resolved computational fluid dynamics (CFD) with scale adaptive turbulence modeling. Wall functions for direct and turbulent entropy production are presented for a cell-centered finite volume method, implemented in the open-source software OpenFOAM and validated on channel, asymmetric diffuser, and periodic hill flow. Single- and two-blade centrifugal pump flow is considered for a wide range of load conditions. Results are compared to experimental data. Time-averaged analysis shows essentially the same loss density distribution among pump components for both pumps, with the impeller and volute region contributing the most, especially in off-design conditions. For both pumps, the losses exhibit significant fluctuations due to impeller–volute interactions. The fluctuation magnitude of loss density is in the same range as flowrate fluctuations and much smaller than pressure fluctuation magnitude. For the two-blade pump (2BP), loss fluctuation magnitude is smaller than for the single-blade pump (1BP). Distinct loss mechanisms are identified for different load conditions. Upon blade passage, a promoted or attenuated volute tongue separation is imposed at part or overload, respectively. In between blade passages, a direct connection from pump inlet to the discharge leads to enhanced flowrate and loss density fluctuations. Future work aims at extending this analysis to stronger off-design conditions in multiblade pumps, where stochastic cycle fluctuations occur. [ABSTRACT FROM AUTHOR]

Settling basins are one of the structures required for removing excess sediment entering irrigation or power canals diverting water from a river. A numerical model is needed to simulate the flow and sedimentation pattern in settling basins. In the current research, a depth-averaged two-dimensional numerical model of flow and sediment is developed using the finite volume method and based on the time-splitting scheme, which also allows for simulating sediment in a non-equilibrium state. The simulation of flow and sedimentation is done by the numerical model in a decoupled method. Sensitivity analysis was applied to estimate the effects of non-equilibrium parameters and the settling velocity on the numerical results. The results revealed that Maleki and Khan's formula and Zhang and Xie's formula are suitable for estimating the suspended load adaptation coefficient and the sediment settling velocity in the numerical simulations. Investigation of the formulas for the bed adaptation length indicated that all three methods considered in the current research had almost equal accuracy in predicting the sediment concentration distribution in the settling basin. The developed model has been verified against two experimental tests, showing a good fit between observed data and the simulated results. [ABSTRACT FROM AUTHOR]

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Shock waves, characterized by abrupt changes in pressure, temperature, and density, play a significant role in various materials science processes involving fluids. These high-energy phenomena are utilized across multiple fields and applications to achieve unique material properties and facilitate advanced manufacturing techniques. Accurate simulations of these phenomena require numerical schemes that can represent shock waves without spurious oscillations and simultaneously capture acoustic waves for a wide range of wavelength scales. This work suggests a high-order discontinuous Galerkin (DG) method with a finite volume (FV) subcell limiting strategies to achieve better subcell resolution and lower numerical diffusion properties. By switching to the FV discretization on an embedded sub-cell grid, the method displays advantages with respect to both DG accuracy and FV shock-capturing ability. The FV scheme utilizes a class of high-fidelity schemes that are built upon the boundary variation diminishing (BVD) reconstruction paradigm. The method is therefore able to resolve discontinuities and multi-scale structures on the subcell level, while preserving the favorable properties of the high-order DG scheme. We have tested the present DG method up to the 6th-order accuracy for both smooth and discontinuous noise problems. [ABSTRACT FROM AUTHOR]

Continental shale oil reservoirs, characterized by numerous bedding planes and micro-nano scale pores, feature significantly higher stress sensitivity compared to other types of reservoirs. However, research on suitable stress sensitivity characterization models is still limited. In this study, three commonly used stress sensitivity models for shale oil reservoirs were considered, and experiments on representative core samples were conducted. By fitting and comparing the data, the "exponential model" was identified as a characterization model that accurately represents stress sensitivity in continental shale oil reservoirs. To validate the accuracy of the model, a two-phase seepage mathematical model for shale oil reservoirs coupled with the exponential model was introduced. The model was discretely solved using the finite volume method, and its accuracy was verified through the commercial simulator CMG. The study evaluated the productivity of a typical horizontal well under different engineering, geological, and fracture conditions. The results indicate that considering stress sensitivity leads to a 13.57% reduction in production for the same matrix permeability. Additionally, as the fracture half-length and the number of fractures increase, and the bottomhole flowing pressure decreases, the reservoir stress sensitivity becomes higher. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the influence of different solder alloy materials on passive devices during laser soldering process. Solder alloy material has been found to significantly influence the solder joint's quality, such as void formation that can lead to cracks, filling time that affects productivity and fillet shape that determines the solder joint's reliability. Design/methodology/approach: Finite volume method (FVM)-based simulation that was validated using real laser soldering experiment is used to evaluate the effect of various solder alloy materials, including SAC305, SAC387, SAC396 and SAC405 in laser soldering. These solders are commonly used to assemble the pin-through hole (PTH) capacitor onto the printed circuit board. Findings: The simulation results show how the void ratio, filling time and flow characteristics of different solder alloy materials affect the quality of the solder joint. The optimal solder alloy is SAC396 due to its low void ratio of 1.95%, fastest filling time (1.3 s) to fill a 98% PTH barrel and excellent flow characteristics. The results give the ideal setting for the parameters that can increase the effectiveness of the laser soldering process, which include reducing filling time from 2.2 s to less than 1.5 s while maintaining a high-quality solder joint with a void ratio of less than 2%. Industries that emphasize reliable soldering and effective joint formation gain the advantage of minimal occurrence of void formation, quick filling time and exceptional flowability offered by this solution. Practical implications: This research is expected not only to improve solder joint reliability but also to drive advancements in laser soldering technology, supporting the development of efficient and reliable microelectronics assembly processes for future electronic devices. The optimized laser soldering material will enable the production of superior passive devices, meeting the growing demands of the electronics market for smaller, high-performance electronic products. Originality/value: The comparison of different solder alloy materials for PTH capacitor assembly during the laser soldering process has not been reported to date. Additionally, volume of fluid numerical analysis of the quality and reliability of different solder alloy joints has never been conducted on real PTH capacitor assemblies. [ABSTRACT FROM AUTHOR]

This study investigates the effects of positive horizontal acceleration of the freestream velocity on a pitch‐oscillating VR‐12 airfoil using computational fluid dynamics. The shear stress transport k–ω model, coupled with a low‐Reynolds number correction, was employed for Re <105 during dynamic stall. The flow equations were solved in two‐dimensional, incompressible form using the finite volume method. The study examined various parameters, including positive acceleration values of the inflow and the angle of attack of the airfoil, to determine their impact on lift and drag coefficients, as well as the C l / C d ${C}_{{\rm{l}}}/{C}_{{\rm{d}}}$ ratio. Additionally, the maximum lift coefficient was analyzed under different inflow and airfoil motion conditions. The results indicate that aerodynamic force coefficients and the C l / C d ${C}_{{\rm{l}}}/{C}_{{\rm{d}}}$ ratio are influenced by both the attack angle and the acceleration of the inflow. Furthermore, inflow acceleration affects the onset of dynamic stall conditions. Generally, inflow acceleration modifies the lift coefficient of the airfoil during the upstroke, while having minimal effect on the drag coefficient, except near dynamic stall points. The findings also suggest that, for a specific airfoil, the sequence of factors with the greatest influence on lift force generation before static stall occurs is as follows: asymmetric airfoil oscillation, symmetrical airfoil oscillation, accelerated inflow, constant velocity inflow, and static airfoil. [ABSTRACT FROM AUTHOR]

Hybrid nanofluids are employed to enhance the antibacterial effect produced by solar radiation. Antimicrobial properties are present in metal nanoparticles (such as silver, copper, or zinc) or metal oxides (such as titanium dioxide or zinc oxide) when exposed to solar radiation. Nanomaterials that have antimicrobial properties are selected from the available literature. A solar sheet with an inclined plane has been chosen and filled with tri‐hybrid nanofluids (THNFs). Hybrid nanofluids including (CuO), Copper oxide, TiO2 (Titanium oxide), and SiO2 (Silicon dioxide), are selected from metal and metal oxide classes including water as a base fluid. The antimicrobial action caused by solar radiation is enhanced by the slip boundaries and variable porous space. The influence of flow and thermal fields on isotherms, velocities, flow lines, and Nusselt numbers are considered. The transformed system of differential equations is solved by the Control Volume Finite Element Method (CVFEM) and RK‐4 technique. The nanoparticulate volume fraction of CuO, TiO2, and SiO2 is largely responsible for the enhancement in the heat transfer rate (HT), as observed. Improved thermal performance is achieved through the flow of THNFs, which in turn acts as an antimicrobial agent. Increasing values of (ϕ=ϕ1+ϕ2+ϕ3,M,Ec,Rd,Q)$(\phi = {\phi }_1 + {\phi }_2 + {\phi }_3,M,Ec,Rd,Q)$ parameters lead to an improvement in the heat transfer rate, which in turn decreases microbial activity. [ABSTRACT FROM AUTHOR]

This study investigates multiphase flow with non-Newtonian fluid at pore scale, using the Compressive Continuum Species Transfer (C-CST) method in a microchannel and 2D porous media, with emphasis on drainage and mass transfer between fluids through the Volume of Fluid (VOF) method. The object of study is the multiphase flow in oil reservoirs, where immiscible fluids coexist in the porous media. The use of recovery methods becomes relevant in scenarios of low reservoir energy or when the physical properties of the oil compromise the flow. The influence of petroleum rheology, especially heavy crude oil with non-Newtonian viscoelastic behaviour, is considered. Recovery methods, such as the injection of CO2, aim to optimize the flow by modifying the rheological properties of the fluid. This article aims to conduct a numerical analysis using the C-CST method with Direct Numerical Simulation (DNS) and volume tracking techniques to capture an interface between fluids. The main objective is to numerically implement a non-Newtonian rheological model in the linear momentum conservation equation, comparing the flow between non-Newtonian and Newtonian fluids at pore scale, and analysing the mass transfer at the flow interface with this new approach. Article Highlights: Numerical study of drainage and mass transfer using the Giesekus model as a constitutive equation. Simulations made in a microchannel and a 2D complex porous medium using the finite volume method. Thin film and mass transfer coefficients change with the Deborah number. [ABSTRACT FROM AUTHOR]

Thermal simulation of a Printed Circuit Board (PCB) can help identify potential overheating risks in the circuit. The proposed modeling method combines analytical temperature solutions and numerical approximations. Only Fourier-series analytical solutions related to the prepreg-layer surfaces need to be calculated, rather than the entire structure. Heat transfer through the lateral sides of a PCB is approximately considered as part of the compensated heat flux of the insulating-layer surface boundaries. Heat diffusion within or between metal layers is numerically approximated using the finite volume method. The core layer is treated as "thermally-thick". Temperature-dependent boundary conditions are considered through iterations. A test solver was developed based on the method. The modeling accuracy was validated by comparison with COMSOL Multiphysics for a four-layer structure with a moderate degree of discretization. Additionally, a PCB for generating DC 3.3V was designed, tested, and modeled, with the modeling results confirmed by the thermal images. The electro-thermal analysis of the distribution of electric potential and Joule heating in traces and vias was integrated into the PCB model. The layout maps of the PCB were further adjusted to reduce Joule heating in the output circuit, and the improvement on reducing the IR drop and hotspot temperature was examined. [ABSTRACT FROM AUTHOR]

This study explores hydrogen production via steam methane reforming (SMR) within complex Voronoi catalytic foams. Pioneering pore-scale analysis unveils the intricate interplay between foam geometry and SMR performance, surpassing conventional macro-scale studies. The highly intricate Voronoi foams intrigue due to their maximized surface area and efficient heat transfer. The research meticulously examines the combined effects of various factors like inlet velocity, temperature, foam properties, and steam-to-carbon ratio on hydrogen yield. Employing OpenFOAM's finite volume method, pore-scale simulations were conducted. Each investigated parameter significantly impacted hydrogen production, with temperature boasting the most remarkable influence. A 142.5% surge in hydrogen production was observed when increasing the temperature from 1100 to 1200 K. Lengthening the foam from 5 mm to 10 mm yielded a 90% increase. This groundbreaking study highlights the immense potential of Voronoi foams to revolutionize SMR processes, paving the way for cleaner and more sustainable energy solutions. [Display omitted] • The SMR process is simulated in a catalytic environment with pore-scale perspective. • Effect of velocity, temperature, S/C ratio & porosity on H 2 generation is analyzed. • Temperature has a greater impact on hydrogen mass flow rates. • Voronoi catalytic foam structure can highly affect heat transfer & hydrogen production. • 90% increase in hydrogen production rate observed by doubling the length of the foam. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of natural convection in an annular cavity filled with a hybrid nanofluid under the influence of a magnetic field. This study is significant for applications requiring enhanced thermal management, such as in heat exchangers, electronics cooling, and energy systems. The inner cylinder, equipped with fins and subjected to uniform volumetric heat generation, contrasts with the adiabatic outer cylinder. This study aims to investigate how different nanoparticle combinations (Fe3O4 with Cu, Ag, and Al2O3) and varying Hartmann and Rayleigh numbers impact heat transfer efficiency. The finite volume method is employed to solve the governing equations, with simulations conducted using Fluent 6.3.26. Parameters such as volume fraction (ϕ2 = 0.001, 0.004, 0.006), Hartmann number (0 ≤ Ha ≤ 100), Rayleigh number (3 × 103 ≤ Ra ≤ 2.4 × 104), and fin number (N = 0, 2, 4, 6, 8) are analyzed. Streamlines, isotherms, and induced magnetic field contours are utilized to assess flow structure and heat transfer. The results reveal that increasing the Rayleigh number and magnetic field enhances heat transfer, while the presence of fins, especially at N = 2, may inhibit convection currents and reduce heat transfer efficiency. These findings provide valuable insights into optimizing nanofluid-based cooling systems and highlight the trade-offs in incorporating fins in thermal management designs. [ABSTRACT FROM AUTHOR]

In the present work, the efficacy of placing comma-shaped pin fins in a minichannel heat sink is studied. The effect of different geometrical factors as well as fluid additives are evaluated. Pin fins' distance and aspect ratio at five levels were introduced as a geometrical parameter. Moreover, three fluid additives including nanofluid based water, Micro-encapsulated PCM (MPCM) Slurry and MPCM Slurry with nanofluid at different concentrations were added to the base fluid. Water as a base fluid at 300 K and at five different Reynolds number enters the channel. Eight sets of comma-shaped pin fins are attached to the constant heat flux (100 kW/m2) surface of heat sink to enhance the heat transfer. In the numerical analysis, average temperature, Nusselt number, friction factor, and pressure drop are considered as output elements. The models presented in the current study is simulated using ANSYS Fluent software, which employs finite volume method. Results revealed that, as the pin fin distance increases, the average temperature decreases, and both the Nusselt number and the pressure drop rise. This is due to the specific shape of comma pin fins that intensifies the vortex formation along the channel as the fin distance increases. Furthermore, α =0.8 is an optimum aspect ratio in which the Nusselt number is at the highest value that is about 7% higher than the other cases. It is also concluded that altering the fluid additive augments the heat trasnfer in fluid domain. Among different fluid structures, MPCM slurry has the highest Nusselt number at all Reynolds number while the pressure drop is high as well. Blending MPCM slurry with 15% concentration and nanofluid with 0.1% concentration offers lower average temperature up to 311 K compared to 335 K for pure water. [ABSTRACT FROM AUTHOR]

AbstractIn this paper, local vorticity distribution in micro-cylinder-groups was investigated by finite volume method and the mechanism of local heat transfer around cylinders was explored by using field synergy analysis. The vorticity distribution and local heat transfer performance are different at different positions around the cylinders. In front of micro cylinders, the vorticity has a positive correlation with heat transfer coefficient, and the average field synergy angle is close to 65° with good synergy effect. The vertical and spanwise vortices are generated on the top and side positions, respectively, which are negatively correlated with the heat transfer coefficient. Affected by the end-wall and boundary layer, the vorticity behind the micro cylinders varies at different heights and the vertical vorticity appears near the root position. The vertical and spanwise vortices account for a similar proportion near the upper part of the micro cylinders, and both of them are positively correlated with heat transfer coefficient. Due to the stagnation effect, the heat transfer coefficient in the rear position has been weakened by about 40% compared with the front position. [ABSTRACT FROM AUTHOR]

In polymer membrane fuel cells (PEMFC), the pore microstructure and the effective diffusion coefficient ( D eff ) of the catalytic layer have a significant impact on the overall performance of the fuel cell. In this work, numerical methods to simulate PEMFC catalytic layers were used to study the effect of isotropy ( I xy ) on the D eff . The proposed methodology studies reconstructed systems by Simulated Annealing imaging with different surface fractions of microstructures composed by two diffusive phases: agglomerates and pores. The D eff is determined numerically by the Finite Volume Method solved for Fick's First Law of Diffusion. The results show that the proposed methodology can effectively quantify the effect of isotropy on the D eff for both diffusion phases. Two trends were obtained in the magnitude of the D eff concerning the change in isotropy: (1) an analytical equation is proposed in this article for D eff ≥ 5 % D 0 and (2) numerical solutions are determined for D eff < 5 % D 0. In our analytical equation are both a lineal and a logarithmic sweep. When the surface fraction is ∅ = 50%, the D eff decreases more linearly than ∅ = 10 % at the beginning of the isotropy change, which indicates that small changes in isotropy in the particulate material modify it drastically; under these conditions the diffusion coefficient in the pore is predominant. (3) When the surface fraction is less than 50%, the D eff decreases more exponentially at the beginning and more linearly at the end of the isotropy change, which shows that small isotropy changes in the bar-aligned material drastically alter it. In this trend, diffusion in the agglomerate is less affected by isotropy. The proposed methodology can be used as a design tool to improve the mass transport in porous PEMFC electrodes. [ABSTRACT FROM AUTHOR]

This article introduces a novel fluid–solid interaction (FSI) method designed for high-speed flow scenarios, which addresses the intricate interactions between viscous compressible fluids and elastic solids. The proposed method, grounded in the finite volume method, balances computational efficiency and stability while accurately capturing fluid dynamics and structural elasticity. Validation against experimental and numerical data from previous studies confirmed the algorithm's effectiveness. The validated FSI model is applied to study drag reduction in elastic spikes with lateral jets under hypersonic conditions, highlighting significant changes in flow characteristics due to structural deformation and lateral jets. The study extensively examined the effects of jet total pressure, jet orifice position, and spike material density on drag reduction, deformation, and flow field characteristics. Key findings include the influence of compressible FSI on temperature, pressure, and drag distribution, the benefits of increased jet pressure ratio for thermal protection, the impact of jet position on flow characteristics, and the relationship between spike deformation and material density. This study offers valuable perspectives and effective strategies for structure design and minimizing aerodynamic resistance in superspeed fluid situations. Nevertheless, there are still obstacles to overcome, such as non-linear deformation, thermal coupling, and computational precision, highlighting the necessity for further enhancement of FSI techniques. [ABSTRACT FROM AUTHOR]

Rotor–stator interaction is an inherently unsteady phenomenon in turbomachinery that significantly influences the performance of turbomachinery. Accurate prediction of the unsteady turbomachinery rotor–stator interaction flow remains a great challenge considering computational cost. In the Reynolds-averaged Navier–Stokes framework, the harmonic balance (HB) method emerges as a potential reduced-order modeling technique, offering significant computational savings over traditional unsteady methods, and revealing unsteady flow characteristics that are elusive to the steady mixing-plane method. In this study, a graphical processing unit (GPU)-based solver utilizing the finite volume method is developed to accelerate the computation of the HB method compared to the traditional central processing unit (CPU)-based solver. An implicit data-parallel block-Jacobi lower-upper relaxation (DP-BJ-LUR) method is first proposed to better fit the distinct parallel architecture of GPU. The HB method with different harmonics, as well as unsteady time marching method, is conducted to evaluate the accuracy and acceleration for convergence of the proposed method by a quasi-three-dimensional radial slice case and a full three-dimensional case for National Aeronautics and Space Administration (NASA) Stage 35 compressor. Acceleration performance of GPU-based solver, impact of relaxation steps on the DP-BJ-LUR method, and numerical accuracy are compared in detail. A maximum speedup of 102 times with 1 harmonic and 90 times with 12 harmonics is achieved by the GPU-based solver on a single NVIDIA Ray Tracing Texel eXtreme 3080Ti GPU compared with the CPU-based solver on a single CPU core of Intel® Xeon® Platinum 9242. [ABSTRACT FROM AUTHOR]

This study addresses the challenge of enhancing aircraft maneuverability, particularly for vertical landing and takeoff, focusing on the fluidic aerial Coanda high efficiency orienting jet nozzle that employs the Coanda effect to achieve thrust vectoring. This research advances understanding of the interplay between geometric and fluidic factors in thrust vectoring. Stationary, turbulent, and compressible flow conditions are assumed, employing Favre-averaged Reynolds-averaged Navier–Stokes approach with the standard k-ε model. Computational solutions were obtained using a pressure-based finite volume method and a structured computational grid. The key findings include thrust vectoring enhancement due to an increase in the total mass flow rate, septum position (at no shock wave-related issues), and Reynolds number. In addition, shock wave formation (at specific mass flow rates and septum positions) considerably affects thrust vectoring. These insights are crucial for optimizing Coanda-based nozzle design in advanced propulsion systems, including in unmanned aircraft vehicles. [ABSTRACT FROM AUTHOR]

In order to improve the fluid dynamic lubrication performance of slipper pair of valve distribution (digital distribution) axial piston pump, this paper proposes a theory analytical model of fluid dynamic lubrication for slipper pairs with different surface structures of valve distribution pump and its tribological optimization mechanism of surface microstructure topography. In the model, based on the finite volume method, the least square method combined with the trust region dogleg was proposed to solve the nonlinear system of equations of slipper dynamic balance. The fluid lubrication mechanism of slipper pairs with different surface structures was analyzed, the probability of overturning and eccentric wear of slipper pairs with complex surface structure and the viscous friction torque were quantitatively analyzed, and experimental research was conducted. The results show that the surface microstructure topography has great influence on the fluid lubrication performance of slipper pairs. Compared with before optimization, the friction torque of slipper with single-support belt, double-support belt, and four-support belt is decreased by 8.58%, 13.65%, and 17.07% at most, respectively, but the probability of overturning and eccentric wear of slipper with double-support belt and four-support belt is increased and the oil film becomes thicker. Reducing the friction loss and enhancing the anti-overturning ability of the slipper pair are often difficult to be compatible. The research results lay a theoretical and technical foundation for the optimization of lubrication performance of slipper pair of valve distribution pump. [ABSTRACT FROM AUTHOR]

Population balance equations are widely used to study the evolution of aerosols, colloids, liquid–liquid dispersion, raindrop fragmentation, and pharmaceutical granulation. However, these equations are difficult to solve due to the complexity of the kernel structures and initial conditions. The hyperbolic fragmentation equation, in particular, is further complicated by the inclusion of double integrals. These challenges hinder the analytical solutions of number density functions for basic kernel classes with exponential initial distributions. To address these issues, this study introduces a new approach combining the projected differential transform method with Laplace transform and Padé approximants to solve the hyperbolic fragmentation equation. This method aims to provide accurate and efficient explicit solutions to this challenging problem. The approach's applicability is demonstrated through rigorous mathematical derivation and convergence analysis using the Banach contraction principle. Additionally, several numerical examples illustrate the accuracy and robustness of this new method. For the first time, new analytical solutions for number density functions are presented for various fragmentation kernels with gamma and other initial distributions. This method significantly enhances solution quality over extended periods using fewer terms in the truncated series. The solutions are compared and verified against the finite volume method and the homotopy perturbation method, showing that the coupled approach not only estimates number density functions accurately but also captures integral moments with high precision. This research advances computational methods for particle breakage phenomena, offering potential applications in various industrial processes and scientific disciplines. [ABSTRACT FROM AUTHOR]

This work examines the fluid flow, heat transfer, and thermal hydraulic performance of turbulent flow through a horizontal pipe integrated with TT that has various cut shapes using numerical analysis. In the current investigation, trapezoidal-cut geometry with single and double cuts is adopted. Three-dimensional simulations have been validated using experimental data from the literature. The equations have been solved using the RNG k-ε model and the finite volume method (FVM). With three distinct types of twisted tape (PT, SC, and DC) and TR (4.0, 6.4, and 8) for a heat flux of 5000 W m−2, the computational findings have been carried out in the range of Reynolds numbers 4000 ≤ Re ≤ 8000. Impact of these factors on Nusselt number, friction factor, and thermal performance are explored and compared to plain pipe under similar conditions. The addition of trapezoidal-cut TTs leads to enhanced mixing of fluid due to swirl flow generation. The result shows that average Nusselt number and friction factor are functions of TR. The thermal performance factor (TPF) for double-cut trapezoidal TT is about 1.2–1.65 which is maximum compared to single-cut and plain TT inserts. [ABSTRACT FROM AUTHOR]

This study develops a numerical simulation to assess transient constriction resistance in various semi-infinite flux channel geometries, including circle on circle, triangle, square, pentagon, and hexagon, which are derived from various heat source arrangements in a large domain. Using both isothermal and isoflux circular heat sources in polygonal flux channels, and employing a finite volume method, the study evaluates transient constriction resistance. The research confirms that for different geometries, similar nondimensionalized constriction resistance results are obtained, particularly when using the square root of the source area as the characteristic length and the square root of the constriction area ratio. The study reveals that flux tube shape has a minimal impact on thermal spreading resistance, with the circleon- triangle configuration displaying the largest deviation from a simple circle-on-circle model. These insights advance our understanding of thermal spreading resistance in polygonal flux channels and their applications in thermal engineering, especially in contact heat transfer problems. [ABSTRACT FROM AUTHOR]

In this paper we study the convergence of a finite volume approximation of a convective diffusive elliptic problem with Neumann boundary conditions and L 1 data. To deal with the non-coercive character of the equation and the low regularity of the right hand-side we mix the finite volume tools and the renormalized techniques. To handle the Neumann boundary conditions we choose solutions having a null median and we prove a convergence result. We present also some numerical experiments in dimension 2 to illustrate the rate of convergence. [ABSTRACT FROM AUTHOR]

This study examines how the variability of the Manning coefficient (n) affects the position of hydraulic jumps downstream of hydraulic structures. Using a robust finite volume method and random field theory, the study investigates the impact of spatial variations in n on hydraulic jump characteristics. Two scenarios are considered: one with a stilling basin and one without. Both one-dimensional and two-dimensional spatial distributions of n are analyzed. The results show that without a stilling basin, there are significant variations in the location of hydraulic jumps in the riverbed. The uncertainty in the location of the hydraulic jump is much higher than the uncertainty in the values of conjugate depths. Additionally, one-dimensional spatial distribution of n leads to higher standard deviations in the estimated location compared to two-dimensional distribution. In scenarios with a stilling basin, increasing riprap length causes the hydraulic jump to move upstream, while standard deviation remains constant. [ABSTRACT FROM AUTHOR]

The heat transfer enhancement and the flow characteristics of Multi-Wall Carbon Nanotubes and Silica water-based nanofluids inside micro-cylinder groups are analyzed based on numerical investigations. The simulations of the flow over thirty circular cylinders in an inline arrangement were carried out at low Re numbers (below 300) and volume concentrations ranging from 0.01 to 0.08. The primary objective of this study is to evaluate the Influence of nanofluids on heat transfer enhancement inside micro-cylinder groups. The finite volume method was employed to investigate the effect of nanoparticles, volume concentration, and Re number on the flow and thermal enhancement. The analysis of the resulting pressure drops, Nusselt number variation, temperature distributions, and thermal enhancement factor suggest that the pressure drop and Nusselt number increased with the Reynolds number for both nanofluids. This augmentation is caused by the interaction between the nanoparticles and the wall. Additionally, it was observed that the thermal enhancement factor exceeded 1 at lower nanoparticle concentrations. Notably, the SiC/water nanofluid demonstrated the most significant improvement in heat transfer at a volume concentration of 2%. [ABSTRACT FROM AUTHOR]

The root pass represents a challenge for welders. Being the first pass of the joint, it requires full penetration and is more prone to metallurgical defects. There needs to be a balance between the forces acting on the molten pool to avoid incomplete penetration or burnthrough. Additionally, the hardness in the heat affected zone (HAZ) should not exceed 350 HV, beyond which there is susceptibility to cold cracking. When different thicknesses are present in the joints, it is often thought that greater thicknesses require higher welding energy (the ratio between power and welding speed). This has also been verified in the literature. The present work aims to test if it be possible to weld the root pass of four plates of different thicknesses (7 mm, 10 mm, 12.7 mm, and 25.4 mm) considering a similar welding energy. This would make the parameterization robust, as the welder would not need to change the welding energy to perform the process under different conditions. An experimental evaluation was conducted on shipbuilding steel ASTM A131 DH36 using the GMAW process, evaluating both the geometric characteristics of the weld bead and the microstructure at different thicknesses. Cooling rates were predicted based on an in-house finite volume method (FVM) computational code. The results indicated that although all welds met the main requirement of full penetration, the metallurgical requirement of a maximum hardness of 350 HV in the HAZ was only achieved at thicknesses of 7 mm and 10 mm. This occurred because, in greater thicknesses (12.7 mm and 25.4 mm), the cooling rate was elevated due to the thickness itself and the use of a higher feed rate. Consequently, in the coarse grain heat affected zone (CGHAZ), there was a shift from the ferritic field to the bainitic field. To meet the requirements, it is advisable to adjust parameters, such as increasing weld energy or applying preheat treatment. Another alternative involves planning subsequent passes to induce a tempering effect on the root. In summary, for geometrical purposes, a constant energy can be used, whereas metallurgical objectives might necessitate greater energy input with increasing thickness. [ABSTRACT FROM AUTHOR]

The finite volume method (FVM) is used to numerically investigate the sloshing behaviors of dual liquid tanks with gas inflow in this study. The sloshing process of a single liquid tank is simulated to verify the feasibility of the numerical method. Three different inlet boundary conditions are then discussed in order to obtain a reasonable gas flow rate. The sloshing process of a dual liquid tank with the gas inflow is simulated, and the effects of three different factors on the sloshing behaviors are investigated. The results indicate that the overload, flow rate, and filling ratio can affect the peak value of the impact force acting on the tank wall. The impact force is positively proportional to the overload (1G, 3G, or 5G). An increase in flow rate (50 g/s, 1000 g/s, or 5000 g/s) or a decrease in filling ratio (99.52%, 75.64%, or 63.69%) can increase the size and number of bubbles, leading to intensified sloshing behavior and increased impact force. [ABSTRACT FROM AUTHOR]

This present study is part of the design improvement process of a specified high torque low-speed engine. This work aims at carrying out an in-depth analysis of in-cylinder combustion, mesh sensitivity, and engine performance at supercharge conditions to provide a foundation for the design improvement process of the given engine. The computational fluid dynamic (CFD) simulations are carried out on a 3D sector from-130° to 130° crank angle (CA) by employing appropriate models to represent the different physical and chemical processes and using the finite volume method for solving the governing differential equations. An extensive investigation has been carried out for the choice of base mesh size and the number of local and temporal refinements to capture the phenomena happening in the combustion chamber at diverse temporal and local scales. The present results have been validated against available literature experimental and simulation results. Primary field variables and the well-known four phases of combustion have been studied for gaining in-depth insight into these phenomena. Cylinder average pressure, mean temperature, heat release rate (HRR), integrated heat release rate (IHRR), and emissions of CO2, CO, NOx, HC and soot are presented to assess the quality of combustion. Engine performance analysis has been done in terms of combustion efficiency, gross work, power, torque, and integrated mean effective pressure (IMEP). The base mesh of 1.4 mm may be an appropriate choice during the injection and combustion process spanning throughout around 40° CA from the start of injection while in the remaining simulation duration of around 220° CA base mesh of 2 mm gives a sufficient resolution. It has been found that maximum heat release takes place in Phase-III, the mixing-controlled phase, of the combustion process. More than 98% combustion efficiency has been achieved in all the simulations. Around 99% of the total heat release and emissions production takes place within 60° CA after top dead center (ATDC). [ABSTRACT FROM AUTHOR]

In this work, we analyze non-Darcy two-component single-phase isothermal flow in naturally fractured tight gas reservoirs. The model is applied in a scenario of enhanced gas recovery (EGR) with the possibility of carbon dioxide storage. The properties of the gases are obtained via the Peng–Robinson equation of state. The finite volume method is used to solve the governing partial differential equations. This process leads to two subsystems of algebraic equations, which, after linearization and use of an operator splitting method, are solved by the conjugate gradient (CG) and biconjugate gradient stabilized (BiCGSTAB) methods for determining the pressure and fraction molar, respectively. We include inertial effects using the Barree and Conway model and gas slippage via a more recent model than Klinkenberg's, and we use a simplified model for the effects of effective stress. We also utilize a mesh refinement technique to represent the discrete fractures. Finally, several simulations show the influence of inertial, slippage and stress effects on production in fractured tight gas reservoirs. [ABSTRACT FROM AUTHOR]

This article focuses on the optimal control problems governed by fourth‐order linear elliptic equations with clamped boundary conditions in the framework of the Hessian discretization method (HDM). The HDM is an abstract framework that enables the convergence analysis of several numerical methods such as the conforming finite element methods, the Adini and Morley nonconforming finite element methods (ncFEMs), the method based on gradient recovery (GR) operators, and the finite volume methods (FVMs). Basic error estimates and superconvergence results are established for the state, adjoint, and control variables. A companion operator for the GR method with specific property is designed. The article concludes with numerical results that illustrate the theoretical convergence rates for GR method, Adini ncFEM, and FVM. [ABSTRACT FROM AUTHOR]

In this research, considering the air methodology, an axisymmetric model was developed, validated, and calibrated for the numerical simulation of an Oscillating Water Column (OWC) converter subjected to a realistic sea state, representative of the Cassino beach, in the south of Brazil. To do so, the Finite Volume Method (FVM) was used, through the Fluent software (Version 18.1), for the airflow inside the hydro-pneumatic chamber and turbine duct of the OWC. Furthermore, the influence of geometric parameters on the available power of the OWC converter was evaluated through Constructal Design combined with Exhaustive Search. For this, a search space with 100 geometric configurations for the hydro-pneumatic chamber was defined by means of the variation in two degrees of freedom: the ratio between the height and diameter of the hydro-pneumatic chamber (H1/L1) and the ratio between the height and diameter of the smallest base of the connection, whose surface of revolution has a trapezoidal shape, between the hydro-pneumatic chamber and the turbine duct (H2/L2). The ratio between the height and diameter of the turbine duct (H3/L3) was kept constant. The results indicated that the highest available power of the converter was achieved by the lowest values of H1/L1 and highest values of H2/L2, with the optimal case being obtained by H1/L1 = 0.1 and H2/L2 = 0.81, achieving a power 839 times greater than the worst case. The values found are impractical in real devices, making it necessary to limit the power of the converters to 500 kW to make this assessment closer to reality; thus, the highest power obtained was 15.5 times greater than that found in the worst case, these values being consistent with other studies developed. As a theoretical recommendation for practical purposes, one can infer that the ratio H1/L1 has a greater influence over the OWC's available power than the ratio H2/L2. [ABSTRACT FROM AUTHOR]

The influence of oblique currents in narrow and shallow channels causes the fluid flow around ships to become complex. To analyze the hydrodynamic characteristics of a ship in such channels, it is essential to examine the influence of oblique currents on the ship's hydrodynamic characteristics. In this study, current direction, ship speed, current speed, and water depth were identified as determinants affecting the hydrodynamic characteristics of a ship. Numerical simulations were conducted on a large oil tanker to investigate the effects of these factors on the ship's hydrodynamic characteristics. The viscous fluid flow was modeled using the unsteady Reynolds-averaged Navier–Stokes (URANS) equations in conjunction with the k-ε turbulence model. The URANS equations were discretized using the finite volume method. The numerical results indicate substantial differences in the hydrodynamic characteristics of ships under oblique current conditions compared to still-water conditions. At a current direction of β = −45°, the direction of the sway force is consistent with that of still water's sway force, which is an attractive force. The yaw moment at β = −45° changes from a bow-out moment under still-water conditions to a bow-in moment. Conversely, at a current direction of β = 45°, the sway force shifts from an attractive force under still-water conditions to a repulsive force. The yaw moment acts as a bow-out moment, which is consistent with that observed in still-water conditions. Furthermore, the influence of hydrodynamic characteristics on a ship varies significantly with changes in ship speed, current speed, and water depth. To ensure the safe navigation of ships, it is essential to develop and apply comprehensive strategies and countermeasures that account for practical conditions. [ABSTRACT FROM AUTHOR]

The Laser-Based Powder Bed Fusion (LPBF) process is an additive manufacturing (AM) technique used to fabricate intricate 3D metallic components from fine powder particles. This study presents a 2D semi-analytical model, an algorithm developed by incorporating multiple physical phenomena of the process, i.e., heat transfer, fluid flow, and Marangoni effect for computing temperature and velocity distribution, to estimate the melt-pool characteristics for the single-track melting. The laser input energy has been modelled as a moving Gaussian volumetric heat source, and the fluid flow phenomenon has been formulated by 'Semi-Implicit Method for Pressure Linked Equations' (SIMPLE) method. A set of two-dimensional transient conservation of mass, momentum, and energy equations are discretized as co-located mesh by Finite Volume Method (FVM) and iteratively solved by Alternating Direction Implicit (ADI) scheme to obtain temperature and velocity field. The Pressure Weighted Interpolation Method (PWIM) is incorporated to avoid pressure oscillation and allow the use of co-located mesh for fluid flow, making the model computationally efficient. The model is validated for Ti6Al4V and Inconel 718 alloy with the experimental findings from the literature. The obtained results are in good agreement with an average deviation of 5.78% and 20.07% for Ti6Al4V , whereas for Inconel 718, 7.87 and 19.53% for melt-pool depth and width, respectively, were observed. Subsequently, the melt-pool growth and characteristics influenced by various process parameters are also studied. [ABSTRACT FROM AUTHOR]

Ultra-precision measurement and manufacturing need high-precision machines, just as a photolithography machine needs air bearings. In gas lubrication, the use of compound restrictors with recesses has been widely proven to be an effective method to improve stiffness, which directly affects the accuracy of the machine. However, determination of the structural parameters of recesses is lacking in theoretical models. This paper has established a mechanical property model for a small-scale guideway, which can respond to the variation in force caused by micron-level changes in the recesses' depth. To meet the requirements of high positioning accuracy and movement accuracy, this paper puts forward a high-stiffness guideway without an air tube. In order to improve rotational stiffness and determine the structural parameters of recesses, this paper found a guideway with the optimal gradient depth of recesses. Both AFVM (adaptive finite volume method) research and experimental results show that the gradient depth of recesses could significantly improve the rotational stiffness of guideways without air tubes. [ABSTRACT FROM AUTHOR]

Methods for determining the characteristics of self-acting (aerodynamic) gas bearings have been developed for many years, but many researchers and engineers still question how sophisticated a model of such bearings should be to obtain reliable results. This is the subject of this article, which presents a numerical analysis of aerodynamic gas bearings using two alternative methods: a specialized program based on the finite difference method, and a universal CFD program using the finite volume method. Gas bearings with a nominal diameter of 49 mm, designed for a 10 kW turbogenerator operating at a rotational speed of 40,000 rpm, are analyzed. The vapor of the low-boiling medium, designated HFE-7100, is used as the bearing lubricant. The calculations focus on determining the position of the bearing journal where the bearing achieved the required load capacity and checking the bearing characteristics beyond the nominal operating point. The most important results obtained by the two independent methods are compared, and recommendations are made for those interested in the numerical analysis of self-acting gas bearings. [ABSTRACT FROM AUTHOR]

In this study, a numerical model of a modified air-drying process of apple slices that considers the conjugate heat and mass transfer in the drying chamber is developed. Inside the apple slice sample, the continuum model is incorporated to describe the non-isothermal two-phase transport. The intra- and extra-sample heat, mass, and momentum transfer are coupled to simulate the transportation phenomena inside the drying chamber using the finite volume method implemented in computational fluid dynamic software (COMSOL Multiphysics 6.0). In this manner, temperature, velocity, moisture content of the drying agent inside the chamber, sample temperature, and moisture content distributions can be predicted. The validity of the proposed model is confirmed by a good agreement between the numerical and experimental data in terms of the overall evaporation rate and temperature. The simulation results indicate that the maldistribution of the convective heat and mass transfer resistance on the sample surface is significant. This can be explained by the nonuniform velocity distribution inside the drying chamber. Additionally, both experimental and numerical observations show that the drying process can be divided into two periods: the quasi-constant drying rate and falling drying rate periods. The impact of dryer operational conditions on the drying process is numerically investigated. [ABSTRACT FROM AUTHOR]

A hydrodynamic control model is established in attention to coupling relationships among cable, propellers and robot body of a tethered underwater robot system. In this model the governing equations of umbilical cable and the robot are firstly introduced, then supplementary conditions are coupled into the equations to forming the dynamic mathematical model; finally a hybrid control strategy based on feed-forward negative feedback method for the cable and PID rule for the propellers are integrated in the mathematical model for composing the whole hydrodynamic control model. Both the mathematical model and the control algorithms are proved to be effective and reliable through comparing simulation with the experimental data in existed references. Based on the numerical model constructed in this paper, trajectory tracking of a tethered underwater robot system in different motion combinations are numerically simulated through computational fluid dynamics method. In the numerical simulations, finite difference method is used to solving the kinematic parameters of the mathematical model, while finite volume method is applied on calculating the hydrodynamic forces under a hybrid control manipulations. The robot motion in vertical direction is determined primary by feed-forward negative feedback strategy of adjusting the cable length, while the horizontal movement of the robot is controlled mainly through PID algorithm; The hydrodynamic loading on the robot body are influenced by the flow fields around the robot. Article Highlights: Established the coupling equations with considering dynamic behaviors among propellers, umbilical cable and robot body. Discovered the conversion relation which unrelated to objective factors between the rotating speeds of propellers and the corresponding thrusts. Analyzed the changing rules of hydrodynamic loading on the underwater robot under a hybrid control strategy. [ABSTRACT FROM AUTHOR]

Most of the oil reservoirs in China are fluvial deposits with firm reservoir heterogeneity, where differences in fluid flow capacity in individual directions should not be ignored; however, the available commercial reservoir simulation software cannot consider the anisotropy of the relative permeability. To handle this challenge, this paper takes full advantage of the parallelism of the multi-scale finite volume (MsFV) method and establishes a multi-scale numerical simulation approach that incorporates the effects of reservoir anisotropy. The methodology is initiated by constructing an oil–water black-oil model considering the anisotropic relative permeability. Subsequently, the base model undergoes decoupling through a sequential solution, formulating the pressure and transport equations. Following this, a multi-scale grid system is configured, within which the pressure and transport equations are progressively developed in the fine-scale grid domain. Ultimately, the improved multi-scale finite volume (IMsFV) method is applied to mitigate low-frequency error in the coarse-scale grid, thereby enhancing computational efficiency. This paper introduces two primary innovations. The first is the development of a multi-scale solution method for the pressure equation incorporating anisotropic relative permeability. Validated using the Egg model, a comparative analysis with traditional numerical simulations demonstrates a significant improvement in computational speed without sacrificing accuracy. The second innovation involves applying the multi-scale framework to investigate the impact of anisotropy relative permeability on waterflooding performance, uncovering distinct mechanisms by which absolute and relative permeability anisotropy influence waterflooding outcomes. Therefore, the IMsFV method can be used as an effective tool for high-resolution simulation and precise residual oil prediction in anisotropic reservoirs. [ABSTRACT FROM AUTHOR]