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• Thermal assessment of the Photovoltaic Modules based on the convective model. • The enormous loss of solar energy during operation can be harvested. • Influence of thermal and hydrodynamic boundary layers on the PV Modules. • Skin-friction drag of wind has the least impact on the performance of the Solar panel. • Framed modules are relatively more energy (electrical) efficient than the Frame-less modules. This paper discusses the thermal aspect of two different types of PV modules. The PV modules are categorised into two major groups: Frameless and Framed modules, and designing structure. Apart from the framed structure, thermal behaviour and its implicit effect on the system is also the key factor of the analysis. Two similar classes of modules are relatively examined and thereafter, are compared with differently manufactured (structure-wise) modules. Here, the framed modules, Solarex (pc-Si) and the RWE Schott Solar (pc-Si) are optically similar; whereas the Solar watt (c-Si) and the Duna Solar (a-Si) are frameless modules. A parallel dichotomy is established on the basis of the quality of the modules being used by the energy industry and the thermal response of the modules at the given conditions. The assessment of the PV modules is based upon the angular orientation of wind, thermal diffusivity of surface, thermal conductivity, heat transfer coefficient, inertial effect of surface, drag force, skin friction, and the thermal behaviour at vicinity of PV surface. The energy equation of the thermal boundary layer over the flat plate is used for thermal profiling of the different PV surfaces. From the experimental measurement, the ambience temperature, surface temperature and wind speed have been determined. The qualitative investigation of geometrically as well as structurally different solar modules is performed with the help of ODE45 application. The flow of air is laminar for all the modules and the drag force varies from 1.45 × 10−5 N to 2.10 × 10−5 N. Friction loss due to wind flow is found to be least for the Solar watt, while the wind orientation of 10° North of East keeps the temperature deviation of the surface from its ambience low for all the modules. The effect of the thermal boundary layer is relatively significant for the Solar watt and the RWE Schott solar modules. Hydrodynamic boundary layer formation has been demarcated from thermal boundary using Blasius and Pohlhausen's solutions for momentum and energy equations of fluid past a flat surface. [ABSTRACT FROM AUTHOR]

The fully developed laminar magnetohydrodynamic free convection between two concentric vertical cylinders with Hall currents and heat source/sink, in the presence of the radial magnetic field, are studied. The governing thermal energy and momentum equations are changed into ordinary differential equations whose solutions are determined in closed‐form expressions of the Bessel and modified Bessel functions of order zero. A parametric investigation illustrating the impacts of the Hall current, magnetic field, heat source, and radii ratio has been accomplished graphically to examine the changes in temperature as well as velocity while the Nusselt number, mass flux, and skin friction values have been presented in tabular forms. The results ensure that the Hall current has a strong and direct impact on the flow character, such that the influence of the Hall parameter enhances the velocity fields in the appearance of heat source and sink. The velocity remains almost constant as the Hall parameter value is greater than four. Moreover, the velocity and temperature fields have an increasing tendency due to the heat source and inversely for the heat sink. [ABSTRACT FROM AUTHOR]

The present study investigates the influence of the magnetic field, thermal radiation, Prandtl number, and leading‐edge accretion/ablation on Blasius and Sakiadis flow. The convective boundary condition is employed to investigate the heat transfer. The nondimensional governing boundary layer equations have been solved by the homotopy analysis method for different values of the pertinent parameters. The effects of these parameters on the dimensionless velocity, temperature, skin friction, and Nusselt number are also investigated for various values of relevant parameters affecting the flow and heat transfer phenomena. The most relevant outcomes of the present study are that enhancement in magnetic field strength undermines the flow velocity establishing thinner velocity boundary layer for both Blasius and Sakiadis flows while an increase in accretion/ablation effect at leading‐edge manifests in a deceleration in velocity for Blasius case and the opposite trend is observed for Sakiadis flow. Another important outcome is that an increase in radiation and accretion/ablation at leading‐edge upsurges the fluid temperature leading to enhancement in the thermal boundary layer. For both Blasius and Sakiadis flow, the skin friction coefficient and the heat transfer rate decline with the enhancement of the leading‐edge accretion parameter. The results are compared with the existing data and are found in good agreement. [ABSTRACT FROM AUTHOR]

A mathematical model of convective steady flow over rotating disks in an orthotropic porous medium has been developed and solved the non-dimentional governing equations for flow by the shooting method that uses fourth order Runge- Kutta integration technique and Newton's method. Magnitude of radial velocity of fluid decreases near the surfaces of the disks for increasing value of Reynolds number. Impact of stretching parameters on the radial and tangential velocity profiles is observed. Computational results are presented graphically for various cases of parameters on velocity (radial f' and tangential g ) and temperature profiles and table values are reported for skin friction and Nusselt number along both disks. It is observed that as the Reynolds number increases, the tangential velocity decreases. As we move far away from the disk the effects of physical parameters is not significant. It is seen that when the stretching parameter increases the radial velocity increases initially and when η=0.3 onwards the radial velocity decreases. This type of study finds application in industrial and engineering fields such as turbine engines and electronic power generating systems etc. [ABSTRACT FROM AUTHOR]

Wall disturbances in high-speed turbulent boundary layers induce large-scale motions in the outer region even when the Reynolds number is not sufficiently high for their existence in the case of smooth wall flows. In the present study, we investigate the dynamics of these outer region large-scale motions by exploiting the scale-by-scale energy transport in the spectral space. By scrutinizing the disparity in the budget terms of the turbulent kinetic energy spectra between turbulence over smooth and disturbed walls, we found that the intensification of the large-scale motions in the outer region is statistically correlated with the stronger interaction between the Reynolds stress and the mean shear, i.e. the production term of the turbulent kinetic energy. The corresponding turbulent kinetic energy is then transferred to smaller-scale motions and dissipated by viscosity, whereas the effects of spatial diffusion and mean convection are insignificant and are dimly affected by the wall disturbances. These dynamic processes are roughly irrelevant to the Mach numbers, and processes related directly to the genuine compressibility effects, namely the dilatational motions and mass flux, are trivial. The outer large-scale motions contribute to the skin friction by approximately 19% ∼ 45% compared with 4% in smooth wall cases in terms of the mean kinetic energy transport, suggesting that the drag increment in turbulent boundary layers in the presence of wall disturbances should be partly attributed to their intensification. • Large-scale motions are stronger in supersonic turbulence with wall disturbances. • Turbulent kinetic energy transport in the spectral space is analysed. • The large-scale intensification is related to the turbulent production. • Large-scale motions contribute highly to skin friction disturbed wall cases. [ABSTRACT FROM AUTHOR]

• Using ammonia combustion to reduce drag for the first time. • Ammonia demonstrates superior local drag reduction. • The self-ignition point decides overall anti-drag effects. • The inlet decomposition ratio is not the higher the better. Boundary layer combustion is an effective method to reduce friction in scramjet combustors. In existing research on drag-reducing fuels, hydrocarbons pose challenges related to carbon deposition and emissions. Meanwhile, hydrogen presents significant difficulties in storage and transportation. For the first time, this paper explores ammonia as a drag-reducing alternative. We employed the Reynolds-averaged Navier-Stokes (RANS) method to investigate the characteristics of drag reduction by ammonia combustion in supersonic flow. Numerical results indicate that the local drag reduction by ammonia combustion is better than hydrocarbon and worse than hydrogen compared to existing research. Ammonia exhibits superior potential for drag reduction. However, the overall drag reduction at room ammonia injection temperature is limited due to the significant distance between the ammonia self-ignition point and the injection port. To address this challenge, we proposed two optimization strategies: increasing the ammonia injection temperature and increasing the inlet ammonia decomposition ratio. As the ammonia injection temperature increases, the self-ignition position moves towards the inlet, and the combustion drag reduction region expands upstream. Interestingly, a higher ammonia inlet decomposition ratio does not necessarily lead to a better drag reduction effect. In fact, an excessively high decomposition ratio can inhibit the combustion drag reduction effect. The most effective drag reduction occurs when the ammonia inlet mass fraction is 50%, resulting in a 42.8% reduction in integrated drag compared to the case without NH 3 injection. Overall, this paper offers critical insights into the utilization of ammonia combustion in scramjets to reduce drag. [Display omitted] [ABSTRACT FROM AUTHOR]

The widely used improved delayed detached eddy simulation (IDDES) method is supposed to accurately predict the mean skin friction when it acts as wall-modeled large eddy simulation (WMLES), as claimed by the original authors. This property has been validated in subsonic flows but not in supersonic flows. In this article, IDDES acting as WMLES was assessed in the simulation of supersonic flat plate boundary layers, accompanied by two other hybrid Reynolds averaged Navier Stokes (RANS)/large eddy simulation (LES) methods which were also employed as WMLES, namely zonal detached eddy simulation (ZDES) and a hybrid RANS/LES method with the blending function proposed by Edwards and Choi (HRLMEC), for comparison. The underprediction of mean skin friction is existent in the results of IDDES but negligible in the results of ZDES and HRLMEC when all other settings are identical, presenting a contrast to the original idea of IDDES and some former research in subsonic flows. With the analysis of the shear stress, the underprediction of mean skin friction of IDDES is attributed to the underprediction of total Reynolds stress and turbulent kinetic energy production in the inner layer. Further research shows that, as for the present supersonic flow cases, IDDES can be capable of precisely predicting skin friction, but only if under the same condition the relevant LES, which uses the same subgrid-scale model, can precisely predict skin friction. This suggests that the problems met by IDDES may be essentially due to the intrinsic difficulty of LES to resolve the inner layer of a supersonic boundary layer: when resolving the inner layer of a supersonic boundary layer, LES should be tuned subtly and needs high computational cost, and may be damaged by any faulty factor, including but not limited to numerical resolution.

The current work emphasizes the modelling of the electroosmosis-modulated peristaltic flow of Jeffery liquid. Such flows emerge in understanding the movement of biological fluids in a microchannel, such as in targeted drug delivery and blood flow through micro arteries. The non-Newtonian fluid flows inside a non-uniform cross-section and an inclined microchannel. The effects of wall properties and variable fluid properties are considered. The long wavelength and small Re number approximations are assumed to simplify the governing equations. Debye-Hückel linearization is also utilized. The nonlinear governing equations are solved by utilizing the perturbation technique. MATLAB is used for the solution, velocity, temperature, skin friction, coefficient heat transport, concentration, shear wood number, and streamlines expressions. The obtained result in optimal electroosmotic velocity (or Helmholtz-Smoluchowski velocity) increases from −1 to 6; the axial circulation has substantial momentum. For larger optimal electroosmotic velocity, a subsequent boost in an axial electric field causes a significant deceleration. Further, the study helps biomedical engineers to create biomicrofluidics devices that may aid in carrying biological fluids.

This study focused on active light touch with predefined textures specially-designed for tactile perception. The counter-body material is stainless steel sheet. Three geometric structures (grid, crater and groove) were fabricated by pulsed laser surface texturing. A total number of twenty volunteers participated in the research which contains two parts: perception tests and skin friction measurements. The perception tests focused mainly on the participants׳ perceptual attributes: perceived roughness and perceived stickiness. For the skin friction measurements, a multi-axis force/torque transducer was used to measure the normal force and friction force between skin and counter-surface along with the fingertip position. The results of the predefined textures showed the ability to reduce skin friction due to the reduction of contact area. Moreover, the participants׳ perceptual attributes were greatly influenced by the predefined micro-structures in the light touch regime.

In this contribution, three methodologies based on temperature-sensitive paint (TSP) data were further developed and applied for the optical determination of the critical locations of flow separation and reattachment in compressible, high Reynolds number flows. The methodologies rely on skin-friction extraction approaches developed for low-speed flows, which were adapted in this work to study flow separation and reattachment in the presence of shock-wave/boundary-layer interaction. In a first approach, skin-friction topological maps were obtained from time-averaged surface temperature distributions, thus enabling the identification of the critical lines as converging and diverging skin-friction lines. In the other two approaches, the critical lines were identified from the maps of the propagation celerity of temperature perturbations, which were determined from time-resolved TSP data. The experiments were conducted at a freestream Mach number of 0.72 and a chord Reynolds number of 9.7 million in the Transonic Wind Tunnel Göttingen on a VA-2 supercritical airfoil model, which was equipped with two exchangeable TSP modules specifically designed for transonic, high Reynolds number tests. The separation and reattachment lines identified via the three different TSP-based approaches were shown to be in mutual agreement, and were also found to be in agreement with reference experimental and numerical data.

Direct numerical simulation of fully developed turbulent plane Couette flow (pCf) has been performed to investigate the effect of surface roughness. Flow characteristics in a statistically stationary field are then compared with the smooth pCf data. The present study considers a case, where the bottom wall is fixed, while the top wall is moving with a constant velocity U w in the flow direction. For roughening, square ribs are placed on the stationary wall with a streamwise pitch λ = 5 k , where k = 0.2 h is the roughness height and h is half the height between the walls. In the present study, we examined the flow and pressure fields around the ribs. For the pitch λ = 5 k , a single recirculation zone is observed in the cavity between any two consecutive ribs. In addition, the profiles of the mean data in the channel core region at different streamwise locations are shown to collapse with each other, indicating that the flow is quasi-homogeneous in the streamwise direction. Further, counter-rotating secondary roll cells or Taylor–Görtler-like vortices, which evolve temporally and oriented along the flow direction, are also observed in the rough pCf. In addition, the large-scale turbulent structures are distorted into fine-scale motion around the ribs. Furthermore, the skin friction coefficient and the mean pressure fields are qualitatively similar to a rough Poiseuille flow (with ribs only on one wall). [ABSTRACT FROM AUTHOR]

This paper presents a field study on the uplift bearing capacity of a pre-stressed high-strength concrete (PHC) pile embedded in clayey soil, and on the soil around the PHC pile that was treated with cement paste. The PHC pile was inserted into a pile hole filled with cemented soil by its own weight (by gravity), and the soil compaction effect of a conventionally driven pile induced by the installation process was avoided. The test results showed that: the pile head displacement needed to fully mobilize the uplift bearing capacity of the test piles was about 0.1 D (pile diameter); the ultimate skin friction of the PHC pile–cemented soil interface was much larger than that of the cemented soil–soil interface; the PHC pile and the cemented soil around the pile behaved as an integral pile in the load transfer process; and the measured ultimate bearing capacity of the test piles was 0.91–0.94 times the American Petroleum Institute (API)'s proposed values for piles under compression and 0.79–0.80 times the values calculated with the effective stress method for piles under compression. [ABSTRACT FROM AUTHOR]

The aim of the study of this paper is the application of magneto hydrodynamics in physiological problems to develop a mathematical model for the study of blood flow in the presence of magnetic effect through stenosis arterial segment. Herschel-Bulkley equation has been taken to the non-Newtonian character of blood flow in the presence of applied magnetics effect. The mathematical model is analyzed through graphically and numerically. As blood is an electrically conducting the magneto hydrodynamic principle may be used to decelerate the flowing blood in a human arterial system and treatment of certain cardiovascular disease. [ABSTRACT FROM AUTHOR]

The prediction of hydrodynamic performance of hull coatings with different surface conditions is a challenging task. Moreover, with the emergence of new prototype coatings that are relatively smooth in terms of roughness characteristics, the accurate estimation of their drag is particularly important, as this will enable a good grading of drag reducing benefits of coatings. In the context of coating studies, the experimental methods are considered as the backbone and results obtained from experimental facilities with the required performance will enable accurate scaling of test results to full-scale ship results. Although numerical simulations like computational fluid dynamics have acquired the level of accuracy good enough to replace some of the systematic model testing used for ship design optimization, it is still not evident whether the simulations will be able to replicate the physical reality such as coating type, its roughness and biofilms accurate enough to enable predictions of the power requirements for ships. Therefore, this article gives insight into various coating hydrodynamic testing facilities and methods that are capable of measuring drag characteristics of coatings. The work highlights the details of each method and identifies the concepts and parameters needed to describe, implement and analyze hydrodynamic coating drag measurements. This article also summarizes the merits and demerits of each type of facility based on reports and studies reported in open literature. Finally, the authors propose a recommendation that can be incorporated into the design of the new hydrodynamic facility. [ABSTRACT FROM AUTHOR]

The backpressure propagation mode accompanied by shock-train evolution is investigated numerically in a rectangular duct with an open space. On this basis, the balance mechanism and parametric effects of heat transfer and skin friction for backpressure propagation are revealed to understand the nature of force competition better. As a result, the backpressure propagation mode can be classified into two different flow processes with increased backpressure. In addition, balance property mechanism reveals that both the momentum inside the boundary layer and the shear force which transfers the momentum from the outer core flow to boundary layer are combined to resist the adverse pressure gradient. Further, parametric effect indicates that varying wall temperatures and roughness heights lead to different degrees of changes in balance property. According to quantitative results, both wall temperature and roughness height decrease the local boundary-layer momentum at the starting point of original pressure rise and thus the local adverse pressure gradient wins the force competition. In the subsequently continuous flow, the adverse pressure gradient continues to propagate upstream and then is retarded gradually by the boundary layer with a fuller velocity profile until a new force balance is generated. [ABSTRACT FROM AUTHOR]

Abstract This paper introduces a new theoretical model for obtaining the natural frequency and mode shape of tapered piles in heterogeneous elastic soil subjected to axial static loading. Friction resistance at the pile-soil interface that is significant for long friction piles, yet not covered in the literature, is considered in the model. The differential equation governing the transverse free vibration of the pile-soil system is derived with associated boundary conditions and is solved numerically using Runge-Kutta method combined with the determinant search technique. Numerical examples are presented to elucidate the effect of the tapering and skin friction of pile, pile-soil relative stiffness, soil heterogeneity and axial force as well as the degree of end restraint. Highlights • A theoretical model is proposed for analyzing free vibration of axially loaded tapered piles. • Friction resistance at the pile-soil interface that is significant for long friction piles is considered. • Numerical solution is computed in a matter of seconds and is accurate. • The proposed model is amenable for a wide range of pile and soil properties. [ABSTRACT FROM AUTHOR]

Abstract The compressive bearing capacity of wished-in-place (WIP) concrete piles and pre-bored grouted planted (PGP) piles in dense sand was investigated by means of model tests. In total, three model piles were tested. The load–displacement response, axial force and tip resistance of each model pile were measured in the static load test process. Several conclusions can be drawn from the model test results: the pre-bored grouted planted nodular (PGPN) pile and the pre-bored grouted planted pipe (PGPP) pile have ultimate skin friction 1.23–1.36 times and 1.34–1.46 times greater than the ultimate skin friction of the wished-in-place (WIP) pile, respectively. The tip bearing capacity of the PGP pile is similar to the tip bearing capacity of the WIP pile, and the hyperbolic model of normalized tip resistance (q b / q c) and normalized tip displacement (S b / D) can represent the tip load–displacement response of the WIP and PGP piles well. [ABSTRACT FROM AUTHOR]

• The paper examines the power-law nanofluid flows due to a shrinking sheet with mass transpiration under inclined MHD. • The governing PDEs are similarly transformed into nonlinear ODEs and solved analytically. • The magnetic field significantly increases the magnitude of the skin friction and mass transpiration. • Cu-H 2 O nanofluid is used to examine the entaire calculation. This paper examines the power-law nanofluid flows due to a shrinking sheet with mass transpiration under inclined MHD. The governing partial differential equations are similarly transformed into nonlinear ordinary differential equations and solved analytically. The mathematical model through analytical solutions graphically shows that the flow's dynamics depending on the Chandraselhar number, mass transpiration, nanofluid and inclined angle parameters. The main findings and methods of the present work includes the closed-form exact solutions are examined for some special cases and one of them is an algebraic solution. Specific and quantitative analytical solutions provide important understanding to the boundary layer flow for power-law nanofluid. The present study reveals that the magnetic field significantly increases the magnitude of the skin friction and mass transpiration. Cu-H 2 O nanofluid is used to examine the entaire calculation. Nanofluids are suspensions of nanoparticles in fluids that show significant enhancement of their properties at modest nanoparticle concentration. [ABSTRACT FROM AUTHOR]

• Stoke's second problem is considered for heat transfer investigation. • The steady MHD nanofluid flow through a porous plate is assumed. • Copper as a nanofluid particle and water, as well as ethylene glycol as base fluid particles are chosen. • The fluid flow dynamics are modeled in nonlinear PDEs. • Analytical simulations are performed via the Laplace transform method. • It is demonstrated that EG-Cu nanofluid has a greater heat transport rate than water-Cu nanofluid. Stoke's second problem is a well-known classical boundary layer (BL) issue involving the time-dependent shear flow of viscous fluid about a flat porous plate in the magnetic field. This study has several applications, including chemical engineering, nanotechnology, heat conduction issues, and biological and medical sciences. A theoretical heat transfer (HT) analysis analyzes Stoke's second problem for an MHD time-dependent nanofluid flow through a porous plate. It produces a sinusoidal oscillation that is perpendicular to the flat plate. Copper (Cu) nanoparticles are suspended in water or ethylene glycol (EG), a base fluid. Modeling the fluid flow uses dimensional PDEs, which are then altered into dimensionless forms by adding the proper parameters. With no slip, the resulting non-dimensional PDEs are handled analytically by the Laplace transform approach (LTA). It is demonstrated that EG-Cu nanofluid has greater skin friction and higher HT rate than water-Cu nanofluid. Furthermore, skin friction is reduced by magnetic and porosity parameters, whereas the nanoparticle solid volume fraction and porosity parameters improve HT. [ABSTRACT FROM AUTHOR]

An analytical solution for MHD boundary layer flow of a viscous incompressible fluid over an exponentially stretching sheet is developed in this study. The effect of thermal radiation is included in the energy equation. Through suitable similarity transformations, the governing equations are transformed into a system of nonlinear ordinary differential equations. Homotopy analysis method (HAM) has been used to get accurate and complete analytic solution. This study reveals that the governing parameters, namely, the magnetic and the radiation parameters have major effects on the flow field, skin friction coefficient, and the heat transfer rate. The magnetic field enhances the dimensionless temperature inside the thermal boundary layer whereas reduces the dimensionless velocity inside the hydrodynamic boundary layer. Heat transfer rate becomes low with magnetic and radiation parameters while the friction factor is increased with magnetic field. Moreover, a comparative study between the previously published and the present results in special cases is conducted and an excellent agreement is found between them.

This paper examines the effect of heat generation or absorption on the free convection flow of an incompressible, electrically conducting fluid about an isothermal truncated cone in the presence of a transverse magnetic field. The non-linear coupled partial differential equations governing the flow and heat transfer have been solved numerically, using an efficient implicit finite-difference scheme along with quasilinearization technique. The nonsimilar solutions have been obtained for the problem overcoming numerical difficulties near the leading edge and in the downstream regime, for air (Pr = 0.72). The effects of various physical parameters on skin friction and heat transfer coefficients and, on velocity and temperature are shown graphically for different values of magnetic parameter (M) and heat generation/absorption parameter (Q). It is observed that, magnetic field decreases both skin friction and heat transfer coefficients. The effect of heat generation or absorption is found to be very significant on heat transfer, but its effect on skin friction is negligible.

An unsteady boundary layer free convective flow and heat transfer of a viscous incompressible, microploar fluid over a vertical stretching sheet is investigated. The stretching velocity is assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along the x -axis so that the sheet is stretched, keeping the origin fixed in the micropolar fluid. The transformed highly non-linear boundary layer equations are solved numerically by an implicit finite difference scheme for the transient, state from the initial to the final steady-state. To validate the numerical method, comparisons are made with the available results in the literature for some special cases and the results are found to be in good agreement. The obtained numerical results are analyzed graphically for the velocity, the microrotation, and the temperature distribution; whereas the skin friction, the couple stress coefficient and the Nusselt number are tabulated for different values of the pertinent parameters. Results exhibit a drag reduction and an increase in the surface heat transfer rate in the micropolar fluid flow compared to the Newtonian fluid flow.

Model uncertainty is present in many engineering problems but particularly in those involving geotechnical behavior of pile foundation. A wide range of soil conditions together with simplified numerical models makes it a constant necessity to review the accuracy of the predictions. In this paper, the outputs of some seventy (70) pile axially-loaded tests have been reviewed with a classic numerical model to assess pile deformation. Probabilistic approach has been used to quantify uncertainties coming from soil tests, statistic uncertainty and also from the model itself. In this way, a critical review of the prediction method and a way to quantify its uncertainty is presented. The method is intended to be used in a wide range of engineering problems.