Search

This study examines the forced convection of a micropolar fluid (MPF) flow across a vertical permeable plate inside a porous medium. A similar solution is derived for a scenario involving a constant surface temperature. The system of transformed governing equations is addressed by employing a finite‐difference method. Notably, a parametric analysis is conducted to demonstrate how the Prandtl number, micropolar parameters, Darcy number, inertia coefficient (ξ), skin friction (Cf), and Nusselt number (Nu) impact the system. The results are then presented graphically, while the physical aspects of the issue are assessed. Although a larger Nu produced a high wall heat transfer, the Cf values are decreased as ξ increases. The ξ also reduces the local Nu. Compared with Newtonian fluids, the MPF increases Cf and reduces the heat transfer rate. The outcomes are validated by comparing the current results with other related studies. The results of this study are useful for improving the efficiency of solar panels by enhancing their cooling rate. It is also found that increasing the inertia of MPF leads to an increase in the friction coefficient (Cf) while increasing porosity, microrotation parameter n and Fs decreases (Cf). [ABSTRACT FROM AUTHOR]

During atmospheric entry, super-/hypersonic vehicles cross distinct atmospheric layers characterized by large density variations and thus experience different flow regimes ranging from free molecular, transition, slip, to continuous regimes. Due to the distinct modeling strategy between these regimes and complex physical phenomena appearing near the vehicles (boundary-layer/shock interaction, base-flow recirculation, etc.), assessing their aerodynamic properties may be difficult. The present work focuses on supersonic flows around sharp-base geometries in both continuous and slip-flow regimes and aims at highlighting the influence of both rarefaction degree and base geometry on the vehicles' aerodynamic features. For this purpose, three axisymmetric cone-cylinder geometries with right-angled, rounded, or flared rear parts are considered. Flow visualization, pressure, and drag measurements are carried out at Mach number Ma=4 and Knudsen numbers ranging from Kn=4×10-4 to 1×10-2 in the supersonic rarefied MARHy wind tunnel. The experimental data are compared with numerical results of simulations performed with a continuous-flow Navier-Stokes (NS) solver and two rarefied flows codes: a discrete-ordinate Bhatnagar-Gross-Krook (K) solver and a direct simulation Monte Carlo (SPARTA) solver. While the NS solver overestimates frictional drag as Kn rises, the rarefied K and SPARTA results show satisfactory agreement with experimental data. The latter numerical results highlight the main effects of rarefaction: as Kn increases, shocks become more diffuse, skin friction strengthens (leading to a significant increase in drag coefficients), and the extent of the base-recirculation decreases. Regarding the aft-body geometry, its influence on the base recirculation vanishes with increasing Kn. [ABSTRACT FROM AUTHOR]

The Helix Stiffened Cement Mixing (HSCM) piles are a type of composite pile with peripile hydraulic soil formed by simultaneous grouting during the installation of helical piles. Combining the grouting process with the helical pile increases pile stiffness, improves axial bearing capacity, addresses buckling and corrosion issues of the pile body, and enhances pile skin friction, thereby increasing its bearing capacity. Currently, there has been extensive research on the bearing capacity of HSCM piles in clay soil, but less on their bearing performance in sandy soil. This study investigated the effects of the number of helix plates, grouting pressure, and the location of grouting holes on the axial bearing performance of HSCM piles through laboratory model tests. The pile formation process, load–displacement curve, variation in pile diameter, and load transfer mechanism of each test pile were analyzed. Using a parametric analysis of numerical simulations, the influence of a sandy soil foundation on the bearing capacity of HSCM piles under varying internal friction angles was examined. The results indicated that grouting holes positioned below the first layer of helix plates enhanced the axial bearing performance of HSCM piles; additionally, increasing the number of helix plates and grouting pressure appropriately also enhanced the axial bearing performance and increased the pile body diameter, positively affecting the pile formation. Additionally, HSCM piles functioned as friction end-bearing piles in sandy soil, with the vertical load at the top of the pile primarily borne by pile end resistance at the limit state of bearing capacity. With increasing internal friction angles and dilation angle, the bearing capacity of the pile foundation exhibited a rising trend. [ABSTRACT FROM AUTHOR]

A non-similar Keller Box analysis of magnetochemically radiative Buongiorno's nanofluid flows past a stretched surface is presented in this work. It offers insightful information for raising the effectiveness of heat, and mass transmission. Numerous scholars have examined various topics, including radiation, porosity, aligned magnetic fields, mixed convection, and the Forchheimer number when including nanofluids in these flows. However, thermal radiation impact, chemical reaction, and magnetic parameters on Buongiorno's nanofluid through a stretching sheet do not yet have a mention within existing scholarly works. To fill in this knowledge vacuum and provide insightful information about these variables. The investigation uniquely encompasses coupled magnetic properties, chemical reactions, thermal radiation on heat, mass transmission in nanofluids, assimilating Brownian motion, buoyancy ratio, and thermophoresis, offering a comprehensive multi-physics analysis that was not previously explored. By employing the Keller Box method (KBFDM), after being converted into a set of nonlinear ODEs, from the PDEs that govern the flow analysis are solved numerically, MATLAB is utilized to obtain graphs and tabular values. The effects of elements without dimensions, such as heat radiation (0 ≤ R ≤ 1), chemical reaction (0 ≤ Kr ≤ 5), and magnetism parameter (0 ≤ M ≤ 2) on concentration, temperature, and velocity distributions are discussed. Additionally, Nusselt number, Sherwood number, and Skin friction impacts are demonstrated. Velocity depreciates with elevating magnetic parameters. The velocity field experiences a significant boost in response to rising thermal radiation and chemical reaction values. A greater magnetic field causes the concentration profile to rise steadily of nanoparticles. Moreover, as (Kr) raises steadily, velocity appreciates however, temperature and concentration diminish substantially. When the magnetic parameter (M) rises, the Schmidt number (Sc) and skin friction decay. Skin friction and Sherwood number show an upward trend for myriad increasing values of thermophoresis (Nt). The present study shows a compatibility rate of 99.9% with the previous research across different values of Nusselt (Nu) and Sherwood (Sh) numbers. Significantly, higher (Pr) enhances (Cf) and (Sh) because of thicker thermal and thinner momentum boundary layers, while decreasing the (Nu) to inhibit heat transfer. It is noteworthy that, increasing (Sc) elevates (Cf), (Nu) and (Sh) by enhancing fluid viscosity and reducing mass diffusivity, which causes concentration within BL to thicken, and improves shear stress and heat transfer efficiency. Through this work, significant knowledge concerning how to Boost the productivity of chemical processing and thermal control mechanisms in magnetic, radiative environments involving nanofluids can be gained for industrial processes. [ABSTRACT FROM AUTHOR]

The current paper reports the impact of variation of ribs' pitch distance in the case of laminar flow and forced convection heat transfer upon flow characteristics in a rectangular channel experimentally and numerically. The thermal behavior of the ribbed channel with water as a working fluid was measured experimentally and compared to numerical simulations performed using Galerkin finite element method under the same operating and boundary conditions. Numerical analysis has been extended to investigate the entire ribbed channel with the presence of nano-particles in the base fluid to predict the performance of the heat transfer process with interaction with extended geometries. The analysis was done keeping heat flux constant at the bottom boundary condition. The impacts of the rib pitch-to-height ratio (p/e = 2.5, 3.125, 3.75, 4.375, and 5), nano-particle volume concentration (0% ≤ φ ≤ 4%), also Reynolds numbers (427.44 to 1282. 9), were all examined in the present study. The results show a good coincidence between the numerical and experimental study with a maximum deviation was nearly 3%. The main findings show that when the nano-fluid volume fraction increases from 0% to 4%, the average Nusselt number for all aspect ratios increases too. Meanwhile, the average skin friction decreases as the Reynolds number increase for different values of AR. Furthermore, the results revealed that the water – aluminum oxide nano-fluid with the concentration φ = 0.04 aid to improve the coefficient of heat transfer by 5% higher than the case of φ = 0.02, and up to 9.4% compared to pure water (φ = 0) due to an increase in viscosity. Finally, the current work shows that these extended surfaces with the use of nano-fluids can remarkably improve heat transfer properties with barely increased friction, making them suitable candidates for the development of efficient heat exchanger devices. [ABSTRACT FROM AUTHOR]

Research Problem: The importance of improving the temperature properties of commonly used fluids in industrial processes is being addressed in this research. Nanofluids, which are composed of extremely small particles dispersed in common liquids such as water or petrol, are the main subject of this area of study. Using a vertically stretchable surface subjected to thermal radiation, the study examines the heat transfer behavior and efficiency of nanofluids.Methodology: Nanofluids that convey heat are studied by applying the fundamental rules of fluid physics to the variables that control their motion. To measure the amount of energy transferred, a nanofluid model is used. Similarity transformations are used to convert the system’s differential equations into ordinary differential equations (ODEs). The subsequent set of nonlinear ODEs is solved using numerical methods. Utilizing graphical analysis, patterns of velocity and temperature may be seen, and their responses to changes in other parameters can be investigated.Implications: This research has important implications for our knowledge of how nanofluids act in heat transfer applications, especially when exposed to thermal radiation and working with vertically stretchy surfaces. The effects of flow direction and thermal conductivity on distributions of velocity and temperature were elucidated, among other important results. More effective heating and cooling systems may be possible as a result of these findings, which have consequences for improving heat transfer processes in industrial environments.Future Work: To better understand how nanofluids behave in heat transfer applications, future studies might investigate more complicated situations and boundary circumstances. It may be possible to optimize nanofluid formulations by studying the impact of various nanoparticle kinds and concentrations on heat transfer efficiency. Research could be more applicable to real-world industrial processes if the numerical results were experimentally validated. [ABSTRACT FROM AUTHOR]

The current study focuses on the flow actions of two-dimensional hybrid nanofluids when they pass through a stretching sheet with viscous dissipation. The hybrid nanomaterials under consideration are Ag + Al,03 and Cu + TiO2, having H:zO functioning as the base fluid. A similarity transformation is utilized to simplify the governing model by switching the partial differential equations (PDEs) into a non-dimensional ordinary differential equation (ODE) system. The study explores changes in volume fraction (0), velocity power index (m), wall thickness parameter (a), and Eckart number (Ec) through graphical representations of entropy generation, thermal and velocity profiles. Remarkably, the velocity field exhibits a substantial increase when these relevant parameters are promoted. In this investigation, the Homotopy Perturbation method is employed to solve the nonlinear ODEs resulting from the study. This technique offers a direct and efficient approach to tackling the problem. The numerical data for the Nusselt number and skin friction coefficient of hybrid nanofluids are shown in a table. [ABSTRACT FROM AUTHOR]

This study investigates the influence of deflector length on the aerodynamic drag and flow characteristics of a standard 25° Ahmed body by a numerical approach. Two class of deflector was selected for investigation to elucidate the impact of angles parameter on both drag and flow characteristics. The first class has a fixed length of 9% of the slant's length and spanning angles from -25° to 25°. The second one has length varying from 0% to 100% of the slant's length deflectors and angles from -5° to 5°. Reynolds Average Navier-Stokes equations with the generalized k-ω (GEKO) model were selected. The numerical methods were conducted with the help of Ansys Fluent software. The numerical parameters of the model were adjusted to obtain the satisfying results of flow and drag. Numerical results were verified by experimental data at similar flow conditions. It was shown that the -5° defector allows for a reduction drag for all lengths tested with a maximum reducing drag of 19%. At the 5° deflector, 14% of the drag reduction was observed when its length is 0.3 length of the slant. For longer deflector lengths, the drag increases again. The deflector shows a good passive technique for drag reduction. However, parameters of the deflector should be carefully investigated and selected. The detailed skin-friction structure, pressure distribution, and wake flow fields relating to the drag behavior are analyzed in this study. [ABSTRACT FROM AUTHOR]

This study employs finite difference modelling to investigate the natural convection of a two-phase hybrid nanofluid consisting of Al[Formula: see text]O[Formula: see text] and Cu nanoparticles dispersed in water along a vertically heated wavy surface. The hybrid nanofluid has unique features that influence convective heat transfer. Numerical solutions analyze fluid flow patterns and temperature distributions, providing insights into heat exchange and thermal management. The research highlights the importance of hybrid nanofluids, notably those containing Al[Formula: see text]O[Formula: see text] and Cu in a water base, in improving overall heat transfer efficiency. The mathematical model accounts for laminar and incompressible fluid flow with a Prandtl number of Pr = 6.2, Lewis number Le = 10, and maximum [Formula: see text] concentration of hybrid nanoparticles. After transforming the governing equations into a non-dimensional form, the implicit finite difference method is used to solve them. The solution employs the in-house FORTRAN 90 code and compares its outcomes with the benchmark results. Various parameters, such as the Schmidt number (Sc = 1 to 10), volume fraction of nanoparticles ([Formula: see text] to 0.1), wavy amplitude (A = 0.0 to 0.3), and [Formula: see text] = (0.05 to 0.2), are investigated regarding temperature, velocity, local skin friction coefficient [Formula: see text], local Nusselt number (Nu), streamlines, and isotherms. Elevated volume fraction generally decreases skin friction, increases temperature, and may reduce velocity. Meanwhile, higher skin friction, temperature, velocity, and local Nusselt numbers often correlate with elevated Schmidt numbers. Changes in amplitude and [Formula: see text] affect skin friction, temperature, velocity, and local Nusselt numbers, providing information on the dynamics of fluid systems. For example, when the volume fraction (ϕ) increases from 0 to 0.1 at Y = 2, the temperature rises by [Formula: see text], while the velocity gradually decreases by [Formula: see text]. This is in contrast to findings according to when the [Formula: see text] rises from 0.05 to 0.2 at Y = 1. In this case, the temperature drops by [Formula: see text], followed by a [Formula: see text] fall in fluid velocity. Understanding these interactions enhances comprehension of heat transfer and fluid dynamics. By investigating these interactions, we not only improve our understanding of heat transfer and fluid dynamics, but also open the door to new strategies for improving thermal systems and manufacturing procedures.

This manuscript merits at examining of an embedded orthogonal plate inside porous domain exposed to uniform heat influx to elaborate on how micro polar fluid factors and permeability characteristic affect the local skin friction, heating rate, and angular velocity inside boundary layer. The plate is subjected to forced convective micro polar fluid influx under steady, incompressible, and viscous circumstances. To facilitate dependable numerical solution, similarity approach is implemented to mutate set of coupled governing equations relevant to the adopted study into a constrained dimensionless differential equations. Computational analysis has been executed hiring Runge-Kutta scheme by Matlab function bvp4c to settle the governing equations. Study's results are highlighted graphically the impact of micro polar fluid factors on the local skin friction, heating rate, and angular velocity curves. High degree of acceptability of present findings compare with prior research results. It is found that the rising of Darcy parameter drives to decrease linearly both heating rate and local skin friction. Among the examined factors, the benchmark parameter of decreasing skin friction is the porosity. Additionally, it is found that an increasing of Prandtl number and micro rotation element lead to enhance Nusselt number. Once curves of micro rotation are interfered at certain distance from the plate due to increase in porosity, Darcy, Forchheimer's, and microelement rotation, the micro rotation curves are inverted.

The author has presented results of numerical modeling of the influence of the angle of attack of a thin width-limited plate with a short chord on the velocity field of the internal region of a turbulent boundary layer (TBL) and skin friction. The computations were performed by the large eddy simulation (LES) method at the Reynolds number Reθ = 540 calculated from the velocity on the channel axis and the momentum thickness. Changes in the average and pulsation characteristics of the three-dimensional velocity field under the impact of the wake of the plate and of tip vortices as functions of the angle of attack of the plate in the range ±1° have been analyzed. It has been shown that a determining influence on the formation of the velocity field is exerted by the tip vortices whose vorticity is opposite with the positive and negative angles of attack. The mean value of the skin-friction coefficient decreases by 6% at the positive angle of attack and by 14% at the negative angle with respect to the value of this coefficient in an unperturbed TBL. [ABSTRACT FROM AUTHOR]

This study investigates standard vehicles' flow behavior and drag during crosswind conditions by a numerical approach. The model is a half-scaled Ahmed body with a slant angle of 25°. Reynolds Average Navier-Stokes equations with turbulent model k-ω SST is applied to solve Navier Stokes equation by discrete method. Experimental data validated the numerical results at the same flow conditions. The results indicated that the model's drag increases with yaw angles, which is connected with the development of the longitudinal vortex on the windward side. However, the lift coefficient and pressure drag acting on the slant showed a maximum value at a yaw angle of around 35° before they dropped again. The drop of those coefficients results in the moving upward of the longitudinal vortex above the slant. The complex vortex structures around the base in both cross-sectional and symmetric planes are analyzed. The skin-friction pattern and pressure distribution on the slant are exposed to understand the effect of the yaw angle on aerodynamic forces. [ABSTRACT FROM AUTHOR]

The enstrophy convection velocity (denoted by u Ω) in the evolution equation of the boundary enstrophy is proportional to skin friction (denoted by τ) in an incompressible viscous flow, which can be determined globally as an optical flow problem from a time sequence of the boundary enstrophy fields. The correlation coefficient between | u Ω | and | τ | is evaluated in a turbulent channel flow at the friction Reynolds number Re τ = 180 , which is about 0.73 in the region of interest containing near-wall strong wall-normal velocity event associated with a sweep-ejection pair) and is approximately independent of the wall-normal coordinate in the viscous sublayer. This correlation coefficient is contributed mainly by strong near-wall coherent structures with high boundary enstrophy. The statistics of the difference between the normalized | u Ω | and | τ | are discussed. The statistical correlation between u Ω and τ elucidates the connection between near-wall flow structures and skin friction. [ABSTRACT FROM AUTHOR]

The objective of the study was to evaluate the load-settlement behaviour of piles, both with and without the inclusion of a sponge material at the pile base to minimize tip resistance and enhance skin friction. Laboratory experiments were conducted to examine the response of pile models subjected to axial loads in dry sand. Physical scaling principles were meticulously applied to determine model pile dimensions and tank size, which were dependent on the material properties of the model. The modelled pile, fabricated using aluminium, had an external diameter of 60 mm. The investigation encompassed pile length-to-diameter ratios of 4 and 6. Axial loads and skin friction were quantified using strain gauge measurements. Furthermore, numerical modelling of the experimental tests was conducted using PLAXIS 3D, where the sand was represented using a hardening soil model and the pile was modelled elastically. Triaxial tests were performed on sand samples to characterize soil properties, and laboratory tests were executed to ascertain pile parameters. To account for soil-pile interaction, interface elements were introduced between the soil and pile. Multiple parametric studies were undertaken by varying pile configurations, and subsequent numerical results were systematically compared with the experimental findings. Numerical models correctly represented pile's behaviour under various loading circumstances. Less than ± 5% of displacement difference was detected between experimental and numerical findings, demonstrating acceptable agreement between the two methods. [ABSTRACT FROM AUTHOR]

Due to dynamical applications of nanoparticles in various engineering and biomedical applications, our work focuses on examining and exploring the numerical study of bioconvected unsteady Williamson fluid flow at a heated permeable stretched sheet in a porous medium, along with the existence of particular Cattaneo–Christov heat and mass flux, viscous dissipation, activation energy, Brownian and thermophoresis motion. A mathematical model has been developed by considering the effects of the aforementioned terminologies on the flow field which are expected to be similar to the physical behavior and already published work. By using suitable similarity transformations, the system of the flow field is transformed from partial differential equations to ordinary differential equations. The developed differential system is then solved numerically through bvp4c in the computational software MATLAB. The tabular and graphical analysis have been presented against velocity, temperature, concentration, and density profiles that imply the impact of physical parameters. The skin friction coefficient, rate of heat, and mass transfer are also examined. The results coincide very well to previous published work for limiting cases that authenticate the validity of the current work. It was observed that upon increasing magnetic field (M) and porosity (Kp) parameters, the velocity profile decelerates but the opposite behavior was seen for motile density, concentration, and temperature profiles. The temperature and concentration of Williamson nanofluid reduced by enhancing the significant thermal and mass stratification. The concentration profile declines for rising values of Schmidt number (Sc), the chemical reaction rate (σ), and temperature difference (δ) parameters but accelerates for higher values of Activation energy (Ea). Also, by increasing Peclet number (Pe), bioconvection Lewis number (Lb), and microorganism concentration difference parameter Ω motile density profile decreases. Analyze the impacts of bioconvection and activation energy on Williamson nanofluid. We numerically imitate the outcomes of viscous dissipation, bioconvection, and activation energy at a heated permeable stretched sheet. We examine the effect of A, M, We, Kp, and S on − 1 2 C f (R e) 1 2 . We examine the effect of M, Kp, and We on S h x (R e x) − 1 2 . We examine the effect of the local density number with M, Kp, We, A, and injection and suction parameters. [ABSTRACT FROM AUTHOR]

In this investigation, an infinite flat plate is employed to examine the flow behavior of Casson fluid and the associated heat transfer phenomena. The plate undergoes an initial acceleration with a constant velocity until it eventually decelerates to rest. The energy equation incorporates the effects of viscous dissipation. An appropriate similarity transformation transforms the governing equations into coupled nonlinear ordinary differential equations (ODEs). A closed-form solution for the velocity profile is obtained, while the energy equation is solved using the built-in function NDSOLVE in Mathematica. The study investigates the influence of governing parameters on dimensionless velocity, temperature, skin friction, and local heat transfer rate under two thermal boundary conditions: Newtonian heating and convective boundary conditions. The fluid's thermophysical properties remain constant throughout the study, with the surface temperature of the plate assumed to be fixed at a constant value. A graphical analysis examines the flow behavior and temperature distribution, revealing the impact of non-dimensional parameters. This study reveals that thermal boundary conditions significantly influence heat transfer rates, with Newtonian heating leading to an increase and convective heating causing a decrease. This is attributed to the direct application of heat at the boundary in Newtonian heating, which enhances thermal energy transfer. In contrast, convective heating disperses heat through fluid motion, limiting transfer rates.

Abstract This paper describes a theoretical method for reconstruction of the skin friction topology in complex separated flows, which is developed based on the exact relation between skin friction and surface pressure through the boundary enstrophy flux (BEF). The key of this method is that a skin friction field is reconstructed from a surface pressure field as an inverse problem by applying a variational method. For applications, the approximate method is proposed, where the composite surface pressure field is given by a linear superposition of the base-flow surface pressure field and the surface pressure variation field and the base-flow BEF field is used as the first-order approximation. This approximate method is constructive in a mathematical sense since a complex skin friction field in separated flows can be reconstructed from some elemental skin friction structures (skin friction source/sink, vortex and their combinations) by a linear superposition of some simple surface pressure structures. The distinct topological features, such as critical points, separation lines and attachment lines, naturally occur as a result of such reconstruction. As examples, some elemental skin friction structures in separated flows are reconstructed in simulations, and the skin friction fields in shock-wave/boundary-layer interactions (SWBLIs) are reconstructed from pressure sensitive paint (PSP) images obtained in wind tunnel experiments.

Birds adapt to the changing flight conditions by performing intricate feather-movements to manipulate the airflow. The avian wings often undergo seamless transformations at the trailing-edge to achieve camber-reflexes for extended flight envelope. A novel bionic flap is introduced on a blade section having S809 airfoil profile, inspired by the avian wings. It produces non-linear smooth wave-like deformations at the trailing-edge to enact spanwise morphing. The aerodynamic enhancement is evaluated by comparing the performance of morphing- and conventional- flap-integrated blades, over a range of angles of attack: 0°−8°, and flap deflections: 5°−10°. Comprehensive investigations are conducted at the chord-based Reynolds number (Rec) of 0.5 million to analyze the evolution of- pressure and velocity fields, surface flow, skin friction, and velocity fluctuations. The analyses reveal significant influence of variable blade-camber on the aerodynamics, particularly at the moderate angles of attack. The morphing flaps exhibit relatively superior performance in delaying flow-separation, and suppressing Reynolds stress, at all the test conditions. However, aeroacoustic analysis reveals that morphing flaps produce relatively higher broadband noise compared to conventional flaps. Overall, this research establishes supremacy of the proposed spanwise morphing over the conventional hinge-based designs in terms of tailoring and/or achieving optimal aerodynamic performance.

This study employs finite difference modelling to investigate the natural convection of a two-phase hybrid nanofluid consisting of Al $ {}_2 $ 2 O $ {}_3 $ 3 and Cu nanoparticles dispersed in water along a vertically heated wavy surface. The hybrid nanofluid has unique features that influence convective heat transfer. Numerical solutions analyze fluid flow patterns and temperature distributions, providing insights into heat exchange and thermal management. The research highlights the importance of hybrid nanofluids, notably those containing Al $ {}_2 $ 2 O $ {}_3 $ 3 and Cu in a water base, in improving overall heat transfer efficiency. The mathematical model accounts for laminar and incompressible fluid flow with a Prandtl number of Pr = 6.2, Lewis number Le = 10, and maximum $ 10\% $ 10 % concentration of hybrid nanoparticles. After transforming the governing equations into a non-dimensional form, the implicit finite difference method is used to solve them. The solution employs the in-house FORTRAN 90 code and compares its outcomes with the benchmark results. Various parameters, such as the Schmidt number (Sc = 1 to 10), volume fraction of nanoparticles ( $ \phi = 0.0 $ ϕ = 0.0 to 0.1), wavy amplitude (A = 0.0 to 0.3), and $ N_{BT} $ N BT = (0.05 to 0.2), are investigated regarding temperature, velocity, local skin friction coefficient $ (C_{f}) $ (C f) , local Nusselt number (Nu), streamlines, and isotherms. Elevated volume fraction generally decreases skin friction, increases temperature, and may reduce velocity. Meanwhile, higher skin friction, temperature, velocity, and local Nusselt numbers often correlate with elevated Schmidt numbers. Changes in amplitude and $ N_{BT} $ N BT affect skin friction, temperature, velocity, and local Nusselt numbers, providing information on the dynamics of fluid systems. For example, when the volume fraction (ϕ) increases from 0 to 0.1 at Y = 2, the temperature rises by $ 75\% $ 75 % , while the velocity gradually decreases by $ 11.11\% $ 11.11 %. This is in contrast to findings according to when the $ N_{BT} $ N BT rises from 0.05 to 0.2 at Y = 1. In this case, the temperature drops by $ 18.75\% $ 18.75 % , followed by a $ 9.68\% $ 9.68 % fall in fluid velocity. Understanding these interactions enhances comprehension of heat transfer and fluid dynamics. By investigating these interactions, we not only improve our understanding of heat transfer and fluid dynamics, but also open the door to new strategies for improving thermal systems and manufacturing procedures. [ABSTRACT FROM AUTHOR]

Under low Reynolds number conditions, the airfoil is prone to a laminar separation bubble (LSB), which causes problems such as lift drop and drag increase. In this work, the fluorescent oil film was applied to study the leading edge LSB from the perspective of skin friction. The experimental study is carried out on a flat plate with the leading edge LSB under the Reynolds number of 9. 5 × 1 0 5 (the characteristic length of the plate chord). The camera captures the leading edge LSB that is formed by airflow separation and reattachment, and the flow in the bubble is opposite to the free flow. The position of separation and reattachment is determined by the distribution of skin friction, which is consistent with the visual image of the oil film. Applying the Poincare–Bendixson (P-B) index formula to test the topology of the separation bubble skin friction, the quantitative relations between the critical points and the boundary switching points in the closed region of several permeable boundary all confirm this topology law. The results show that the fluorescent oil film can quantitatively map the flow structure of the LSB, and further verify the advantage of this method in the visual measurement of the complex flow structure. [ABSTRACT FROM AUTHOR]

This research article explores the effect of thermal radiation and heat source/sink on a hybrid nanofluid comprising of Aluminium oxide (Al2O3) and Titanium dioxide (TiO2) nanoparticles suspended in the base fluid of water (H2O). The bvp4c algorithm is utilized to solve the governing equations, and the influence of various parameters on velocity and temperature is examined via graphs. It is noted that the magnetic parameter (M) escalates the temperature and increases penetrates the velocity. In addition, the skin friction and heat transfer effects are also discussed. [ABSTRACT FROM AUTHOR]

This paper describes a theoretical method for reconstruction of the skin friction topology in complex separated flows, which is developed based on the exact relation between skin friction and surface pressure through the boundary enstrophy flux (BEF). The key of this method is that a skin friction field is reconstructed from a surface pressure field as an inverse problem by applying a variational method. For applications, the approximate method is proposed, where the composite surface pressure field is given by a linear superposition of the base-flow surface pressure field and the surface pressure variation field and the base-flow BEF field is used as the first-order approximation. This approximate method is constructive in a mathematical sense since a complex skin friction field in separated flows can be reconstructed from some elemental skin friction structures (skin friction source/sink, vortex and their combinations) by a linear superposition of some simple surface pressure structures. The distinct topological features, such as critical points, separation lines and attachment lines, naturally occur as a result of such reconstruction. As examples, some elemental skin friction structures in separated flows are reconstructed in simulations, and the skin friction fields in shock-wave/boundary-layer interactions (SWBLIs) are reconstructed from pressure sensitive paint (PSP) images obtained in wind tunnel experiments. [ABSTRACT FROM AUTHOR]

As a lifestyle habit, shoppers like to lick their fingers before opening the polyethylene (PE) shopping bag. In fact, this implies a scientific problem, that is, moisture has an impact on the friction behavior between the plastic bag and the surface of the finger skin. In this study, an experimental method was employed to measure skin friction at three different hydration levels. The high-density polyethylene (HDPE) and low-density polyethylene (LDPE) materials were performed, and photographs of fingertips touching PE films were recorded by a camera. The experimental results showed that the applied normal load is positively correlated with the friction force and negatively correlated with the friction coefficient. And moisture content will increase friction. Specifically, when the fingertip slides on the HDPE film, the friction coefficient of the water-soaked skin is 5.9 times that of the dry skin. It can be inferred that the decrease in modulus of elasticity, as well as volume expansion, leads to an increase in contact area when the skin is wetted with water. This is the main reason for the increase in finger friction. In addition, a negative power function model was established to describe the relationship between the coefficient and the friction conditions by considering the combined effects of hydration level, normal load and material. Abbreviations: CCD: Charge-coupled Device; COF: Coefficient of friction; HbA1C: Hemoglobin A1C; HDPE: High-density polyethylene; LDPE: Low-density polyethylene; PE: Polyethylene; SC: Stratum corneum; [ABSTRACT FROM AUTHOR]

The current state-of-the-practice technology for high-lift aerodynamic simulations is to solve the Reynolds-averaged Navier-Stokes (RANS) equations on a fixed grid or a refinement sequence of fixed grids. The Fixed-Grid Reynolds-Averaged Navier-Stokes Technology Focus Group set out to determine meshing requirements and best practices, whether RANS can accurately predict the change in aerodynamic performance with changes in flap deflection, whether RANS modeling can produce accurate results near CLmax, and the effects of underconvergence and solution strategy on computed results. Eighteen groups of participants submitted over 100 datasets. Challenges with grid convergence and iterative convergence made it impossible to definitively answer all the questions we had posed. Despite this, we can conclude that meshes with at least half a billion cells (more than one billion degrees of freedom) are required for grid convergence away from stall; that RANS simulations cannot currently be reliably used to predict aerodynamic coefficients near stall, nor changes in coefficients with changes in flap angle; that iterative underconvergence remains a significant source of uncertainty in outputs; and that solution initialization can have an important effect on solution behavior, including flow separation patterns. [ABSTRACT FROM AUTHOR]

A numerical investigation was carried out to evaluate the thermo-hydraulic characteristics of a corrugated channel utilizing both single and hybrid corrugated configurations. The single corrugation configurations consisted of trapezoidal and saw-tooth corrugations, denoted as Single Corrugation-1 (SC1) and Single Corrugation-2 (SC2). In addition, the hybrid corrugated configurations included four distinct arrangements, each combining trapezoidal, saw-tooth, and triangular cavities in different ways, represented as Hybrid Corrugation-1 (HC1), Hybrid Corrugation-2 (HC2), Hybrid Corrugation-3 (HC3), and Hybrid Corrugation-4 (HC4). The flow was considered steady, two-dimensional, laminar with Reynolds numbers (Re = 500–900), while a heat flux of 2000 W/m2 was applied along the corrugated wall. The findings demonstrated that the flow and temperature contours were significantly influenced by both single and hybrid corrugated configurations. All hybrid corrugations showed Nusselt number (Nu) enhancements of 20%–36% compared to SC1 and 40%–60% compared to SC2 at Re = 900. Moreover, hybrid corrugated configurations showed better Thermal Hydraulic Performance (THP) compared to single corrugations. At Re = 900, the THP values for HC1, HC2, HC3, and HC4 were 0.95, 1.12, 1.05, and 1.02 compared to SC1, and 1.26, 1.49, 1.39, and 1.35 compared to SC2. Notably, among all the cases, HC2 demonstrated the most significant increase in heat transfer.

Abstract The objective of this article is to examine the simultaneous incorporation of polymers and dust particles, a previously unexplored topic according to the available literature. Understanding these effects is essential for industrial processes and biomedical engineering applications where the manipulation of drag and heat transfer characteristics is desired. This research looks at how including polymers in a viscous non-Newtonian FENE-P dusty fluid alters the flow and heat transfer characteristics of the boundary layer over a non-linearly stretched surface. By employing an appropriate similarity transformation method, we transform the nonlinear system of equations into an equivalent form that exhibits similarity. The resulting boundary layer equations are then numerically solved to investigate the effect of flow factors on the drag force and Nusselt number. This analysis allows us to investigate how various flow parameters influence the forces experienced by the fluid and the rate of heat transfer. In our investigations, we observe a decrease in velocity and an increase in heat transfer when both polymers and dust particles are present. These results suggest that the presence of polymers and dust particles simultaneously has a positive effect on fluid dynamics and increases the system’s thermal exchange efficacy. [ABSTRACT FROM AUTHOR]

The clothing fabric and skin interact continuously across the many regions of users′ bodies during wear, which can lead to both physical skin damage and discomfort. Therefore, this investigation aimed to explore the regional differences in skin friction, tactile perception, and sensitivity in both females and males during the skin-textile interaction. The static and dynamic friction coefficient and textile perception (texture, stickiness, pleasantness, and discomfort) were measured across the 36 selected testing body areas by using a friction measurement device. The results revealed there was a significant difference in skin friction, tactile perceptions, and sensitivity across the various body regions. The anterior neck had the highest skin friction in both females and males, and participants generally rated higher texture perception in their anterior aspects compared to posterior and lateral regions. There was no significant difference in skin friction, tactile perception ratings, and sensitivity between females and males. Practitioner summary: This study sought to examine regional variations in skin friction, tactile perception, and sensitivity during the skin-textile interaction. There was a significant difference in skin friction, tactile perceptions, and sensitivity across the various body regions and no significant sex effect on skin friction, tactile perception ratings, and sensitivity. [ABSTRACT FROM AUTHOR]

This work purveys an artificial neural network (ANN) model for the steady two-dimensional viscous incompressible radial flow of $Au - Water$ (a mixture composed of water as base fluid and nanoparticles of Gold (Au)) and $Ag - Water$ (a mixture composed by water as base fluid and nanoparticles of Silver (Ag)) nanofluids between plane walls which converge in the presence of the MHD effect. The governing partial differential equations of the present physics and their appropriate boundary conditions are initially cast into dimensionless forms to reduce into the ordinary differential equation. The resulting equation thus formed is worked out by adopting the superior numerical simulation, namely, successive linearization method (SLM) to get the accurate solution, and used to generate the data set of size $1502\times 4$ . A great agreement of the numerical simulation is achieved with the existing results. Two ANN models (Model 1 and Model 2) with two hidden layers were proposed. In Model 1 first hidden layer consists of 5 neurons and the second hidden layer consists of 3 neurons, whereas Model 2 consists of 10 neurons in the first hidden layer and 5 neurons in the second hidden layer. The results showed that the proposed ANN model can predict the velocity with high accuracy, and helps to predict the velocity/skin friction for any combination of the values of the proposed fluid’s physical parameters. An R-squared value reaching 0.99 can be obtained using an artificial neural network with the Stochastic Gradient Descent (SGD) optimizer, with a momentum of 0.8, and a learning rate of 0.02.

Flow of a viscous, incompressible and electrically conducting fluid through an aggregation of porous cylindrical fibrous beds in an axisymmetric direction has been considered. The effect of a uniform magnetic field in the transverse direction to the flow on the overall bed permeability (OBP) has been studied via an effective medium approximation. At the interfaces, continuity of velocity and stress components has been employed. In order to gain some physical insight into the flow pattern, the impact of different parameters governing the flow such as porosity, internal permeability, and the magnetic parameter on the OBP and velocity field has been analyzed analytically as well graphically. The expressions of skin friction at the inner and outer boundaries of the envelope are also derived and their behavior with respect to flow parameters are analyzed through graphs. Results show that the porous core subjected to a normal magnetic field increases the OBP, in the sense that it decreases the filtration time. Thus, the presence of magnetic field gives the flexibility to maintain the OBP of the present model unaffected even when its porosity decreased due to any possible contamination. Under special cases, when the internal permeability tends to zero (solid core), and in the absence of the magnetic field, obtained results validate with already published results.

In this work, we investigate the boundary layer flow suggested by the Falkner-Skan equation for different flow parameters. Using a stream function, the Falkner-Skan equation has been converted into a strongly nonlinear third order ordinary differential equation. To solve the obtained differential equation, we construct an efficient numerical algorithm based on nonpolynomial quartic spline function. Skin friction co-efficent has also been calculated. Finally, to validate the theoretical results obtained and to show the applicability of our constructed algorithm, we have carry out numerical experiments for various parameters with the help of graphs and tables. [ABSTRACT FROM AUTHOR]

In karst areas, the use of bored pile is often limited due to the loss of injected grout slurry. A novel technique is proposed to install a membrane with jet nozzle, through which jet grouting is implemented for expanding the membrane to form good interaction with the surrounding rock. Casting tests are conducted to examine how a membrane deforms subjected to a uniformly applied grout pressure. A mathematical model is derived to estimate the bulb length as a function of grout pressure and water/cement ratio. The critical bulb length is suggested to be 0.8 times the diameter of karst cave. Model-scale laboratory tests are performed on membrane-confined grouted piles under axial loading. The results show that membrane-confined grouted pile can have a much higher bearing capacity by 1.5 times and a much lower settlement by 50% compared to conventional pile. The contributions of skin friction and bulb resistance account for over 90% of the axial resistance, whereas the pile tip resistance is within 10% of the axial resistance. The pile's bearing capacity increases with the bulb length, bulb number and bulb depth. An analytical model is further proposed to predict the load–settlement behaviour of membrane-confined grouted pile for use in practice. [ABSTRACT FROM AUTHOR]

The study of inclined magnetohydrodynamics (MHD) mixed convective incompressible flow of a fluid with hybrid nanoparticles containing a colloidal combination of nanofluids and base fluid is presented in the current research. Al2O3-Cu/H2O hybrid nanofluid is utilized in the current analysis to enhance the heat transfer analysis. The impact of radiation is also placed at energy equation. The main research methodology includes that the problem provided equations are first transformed into non-dimensional form, and then they are obtained in ordinary differential equations (ODEs) form. Then using the solutions of momentum and transfers equations to solve the given ODEs to get the root of the equation. The main purpose includes the resulting equations are then analytically resolved with the aid of suitable boundary conditions. The results can be discussed with various physical parameters viz., stretched/shrinked-Rayleigh number, stretching/shrinking parameter, Prandtl number, etc. Besides, skin friction and heat transfer coefficient can be examined with suitable similarity transformations. The main significance of the present work is to explain the mixed convective fluid flow on the basis of analytical method. Main findings at the end we found that the transverse and tangential velocities are more for more values of stretched/shrinked-Rayleigh number and mass transpiration for both suction and injection cases. This is the special method it includes stretched/shrinked-Rayleigh number, it contributes major role in this analysis. The purpose of finding the present work is to understand the analytical solution on the basis of mixed convective method. [ABSTRACT FROM AUTHOR]