Decrease In Boundary Layer Thickness Research Articles

Analysis of buoyancy features on magneto hydrodynamic stagnation point flow of nanofluid using homotopy analysis method

This study aims to examine the buoyancy features of the magnetohydrodynamic (MHD) stagnation point flow and temperature transfer in a nanofluid flow through a convectively heated stretching sheet. The dimensionless form of the governing model is highly nonlinear ordinary differential equations (ODEs) and solved using the Homotopy Analysis Method (HAM). To obtain series solutions the computational program MATHEMATICA is used. It is found that the fluid velocity and boundary layer thickness decrease when the velocity of the stretching sheet is less than the free fluid velocity. The stretching parameter λ and the buoyancy ratio Nr reflect an increase in the velocity profile f′(η) and a decline in the temperature θ(η) and the concentration profile ϕ(η). The skin friction Cf increases because of the motion of nanoparticles and the Nusselt numbers Nux, reduce with the magnetic parameters and increase with the convective parameters. Increased in the Prandtl, Pr, and Lewis numbers, Le values indicated a faster heat transfer to mass transfer. Additionally, results show that the magnetic field accelerates the mass transfer and enhances fluid flow, leading to a higher Sherwood number (Shx).

Numerical treatment via the spectral collocation method for Casson–Williamson nanofluid flow due to a stretching sheet with slip conditions

The main goal of the research is to investigate the effects of temperature and concentration slip on the MHD Casson–Williamson nanofluid flow through a porous sheet, with a focus on viscous dissipation. This research has a novel approach, as it seeks to incorporate various factors that have not been previously studied in this context. Moreover, an inclined magnetic field from the outside is applied to the stretched surface. Besides this, it is considered that the viscosity of nanofluids depends on temperature while all other physical characteristics are taken to be constant. It is hypothesized that the expanding surface that stretched exponentially is what caused the flow motions of the nanofluid. There are several engineering applications for this type of study, which is based on MHD non-Newtonian nanofluid flow across a stretched surface with heat generation and viscous dissipation. They include solar energy storage, energy distribution, chemical reactors, and the manufacturing of polymers. To examine the heat transmission and mass transfer rates, tools like thermophoresis and Brownian motion were implemented. The flow problem is formally represented as a set of nonlinear PDEs that are then, through the use of dimensionless variables, converted into a set of ODEs. To numerically obtain the solution to the problem, the shifted Chebyshev polynomials of the third-kind approximation along with the spectral collocation technique are utilized. This process transforms the existing model into an algebraic equation system that was created as a restricted optimization problem, which is then optimized to obtain the solution and the unknown coefficients. For a variety of pertinent parameter values, the graphic and tabular representations of the concentration, temperature, velocities, rate of heat mass transfer, and shear stresses of nano-fluids at the surface of the sheet are shown. Finally, there is a remarkable amount of agreement between the earlier investigation and the comparison research that was conducted. The findings suggest that higher values of the magnetic parameter, Casson parameter, viscosity parameter, and suction parameter lead to a decrease in both velocity and boundary layer thickness. Furthermore, an increase in the viscosity parameter, Casson parameter, and magnetic parameter results in elevated values for both temperature and concentration.

Experimental Investigation and Optimization Analysis of a Designed Wastewater Treatment System

Wastewater, crude oil, gas, and solid particles are extracted from underground as products during oil production and there are various methods for treating this wastewater. In this study, a corrugated plate treatment system using the gravitational treatment method was designed as a wastewater treatment method. In the designed system, wastewater (oil–water mixture) was treated using uncoated corrugated plates and corrugated plates coated with hydrophobic material. The effects of hole diameter, length, and curvature angle of the corrugated plates; pumping speed of the mixture into the system; mounting angle of the corrugated plate sets; and the distance between the plates on treatment capacity in the case of using coated and uncoated plates were experimentally investigated. In order to statistically examine the effect of the parameters and the hydrophobic material used on the treatment capacity, the relevant parameters were optimized using the response surface method (RSM) and Box–Behnken design. It was observed that there are significant changes in the treatment capacity due to events (flow treatment, decrease in boundary layer thickness, and change in fluid energy). In addition, it was concluded that coating the plates increased the treatment capacity and the mounting angle of the plate sets in the system greatly affected the treatment capacity.

Numerical study on the scale effect of tip vortex cavitation induced by incoming velocities and scale ratios

Large eddy simulations of tip vortex cavitation (TVC) around an elliptical hydrofoil is performed to study its scale effect. A satisfying agreement is obtained between the numerical and experimental data. It indicates that the scale effect of TVC is remarkable. With the increase of scale ratio or incoming velocity, the intensity of TVC significantly increases. Based on our results, two mechanisms for the scale effect of TVC are proposed, i.e., the roll-up of boundary layer and the interaction between tip vortex (TV), secondary vortex and trailing vortex. As incoming velocity increases, the fusion of TV and secondary vortex enhances and the boundary layer thickness decreases, which lead to larger circulation and smaller vortex core radius, tending to intensify TV. As scale ratio increases, the fusion of TV and secondary vortex enhances and the boundary layer thickness increases slightly, which lead to much higher circulation and slight increase of vortex core radius, promoting the occurrence of TVC in general. In addition, with equal cavitation number and Reynolds number, TVC in the large scale is stronger than that in the small scale, indicating that it seems not so reasonable to equate the velocity-induced scale effect with the scale-ratio-induced one.

Variable fluid properties analysis for thermally laminated 3-dimensional magnetohydrodynamic non-Newtonian nanofluid over a stretching sheet

This article is mainly focused on the viscous flow of cu-water/Methanol suspended nanofluids towards a three-dimensional stretching sheet reformed by magnetohydrodynamic phenomenon. The viscous effect is considered as temperature dependent with water treated as a base fluid. Similarity conversions are employed to set forth the non-linear equations of this physical problem. An innovative model for 3D analysis for cu-water/Methanol nanofluid with an irregular viscosity is presented in the present study. Reynold’s model of viscosity is considered in the present study. Moreover, shooting technique is employed to elaborate the non-linear coupled governing equations with the relevant boundary conditions. The physical interpretation of these numerical calculations is presented through a graphical specimen of velocity, Nusselt number, temperature, and skin friction etc. The results of present model are showing quality harmony with the results of existing model. This model is being used for manipulating and designing the surfaces such as stretching/shrinking wrapping and panting devices in nanotechnology. The results also show the significant changes in flow characteristics with changing the value of stretching parameter. It is observed that with an increasing in nanoparticles volume fraction boundary layer thickness decreases. Further, it is also observed that with an increase in viscosity parameter, temperature increases because here we are considering temperature dependent viscosity.

An implicit Keller box approach for solution of MHD three-dimensional flow through a porous medium

The present study investigates the Soret and Dufour effect on free-convection flow of a viscous incompressible fluid through a porous medium bounded by an infinite vertical porous plate with chemical reaction and viscous dissipation is investigated with aid of Implicit Keller box and regular perturbation methods. The flow is assumed in the presence of transverse magnetic field. Characteristics of Velocity, Temperature and Concentration are obtained and graphical interpretation is made. The observation of these results reflects that velocity and thermal boundary layer thickness decrease with the increase of radiation parameter. Graphical interpretations establish a good agreement in a realistic sense.

Unsteady EMHD free convective second grade fluid flow past an exponentially accelerated vertical porous plate

This paper presents a detailed account of unsteady, incompressible, viscous, electrically conducting, unidirectional, free convective second grade fluid through an exponentially accelerated vertically infinite plate with both applied electric field and magnetic field being present. The equation of motion and energy manifested as nonlinear partial differential equation are represented as algebraic equations using implicit finite difference scheme and solved numerically by implementing the damped-Newton method. With the help of the momentum and energy equation, we defined the expressions for skin friction and Nusselt number. The cases n = 1(constant acceleration) and n = 0.5(variable acceleration) are also taken into consideration. The solution obtained is eventually simulated using MATLAB and the resulting graphs representing the influence of non-dimensional parameters on flow field and temperature field are discussed thoroughly. We have also validated the results obtained from the present methodology with the results obtained from already existing methodologies under some limited cases. It is interesting to note that when the plate is being cooled by free convection current, with increase in viscoelastic parameter the viscous forces are dominated by the elastic effects which results in accelerating the velocity flow profile. For comparatively smaller values of Ec the temperature distribution decreases with increasing Re as the suction propagation facilitates decrease in boundary layer thickness which consequently enhances heat transfer rate. The effect of Ec is to raise the temperature profile due to enhancement in viscous dissipation effects. Practically, the combined effects of the physical parameters are remarkably important in various engineering, medical and industrial applications.

Wall-Resolved Large-Eddy Simulation of Near-Stall Airfoil Flow at

A wall-resolved large-eddy simulation (LES) of the near-stall flow around the Aerospatiale A-airfoil at is conducted. The present LES shows typical Reynolds-number effects compared to the previous LES at , such as the increase in lift coefficient, decrease in boundary-layer thickness, delay of turbulent flow separation, and upstream shift of transition location. Among these Reynolds-number effects, the difference in the development of momentum displacement thickness is focused on and further analyzed based on the integral relation of the boundary layer. This analysis reveals that the different mechanisms of the laminar–turbulent transition between the two Reynolds-number cases cause an initial difference in the momentum displacement thickness. This initial difference is then amplified downstream by the deceleration effects of the mean flow. These results suggest that proper estimation of the laminar and transitional flows near the leading edge is crucial for predicting the trailing-edge stall phenomena and their dependency on the Reynolds number.

Experimental study of wall temperature effect on shock wave/turbulent boundary layer interaction in hypersonic aircraft

The wall temperature effects on turbulent boundary layer and shock wave/turbulent boundary layer interaction are studied experimentally at Ma 2.7 with wall-to-recovery temperature ratio Tw/Tr from 0.67 to 1.2. The high-resolution turbulent flow structures are captured and analyzed by applying the nano-tracer planar laser scattering and particle image velocimetry techniques. The influence mechanisms of wall temperature on the vortices and interaction flow field are explained. The results indicate that under the heating wall condition, the increase of gas viscosity and volume causes the turbulent boundary layer to develop thicker and faster. The thickness increases 0.79 mm as Tw/Tr increases 0.2. The boundary layer shape presents intermittence with large-scale vortices increasing in size and number. The shock wave interaction point moves 1.43 mm upstream as Tw/Tr increases 0.2 due to the increasing boundary layer thickness. More intensive separation of the boundary layer leads to the height and length extension of the separation region and the increase of the separation shock angle. Under the wall cooling effect, the boundary layer thickness decreases, and the global vorticity reduces. The velocity field becomes more uniform. The present study can provide an important experimental reference for the design of hypersonic aircraft.

Mathematical analysis of magnetized Jeffery fluid through a nonlinear stretchable surface with mass analysis and chemical reaction

Non-Newtonian activity has been found in the manufacturing of coated sheets, foods, fibre optics, drilling muds, and plastics polymers. The Jeffery solvent is one of these fluid models that has really piqued the curiosity of scientists. With such a modelling approach, relaxation and delayed responses are possible. The investigation of boundary layer motions across a stretched cylinder has lots of applications in filament activities, crystallization and sheet fabrication, photonic circuits, recrystallization, and other industries. The convective heat transfer motion of a Jeffery non-Newtonian liquid influenced by a stretchy material with thermal performance is investigated in this paper. Applying transformation variables, the Physical quantities are converted to physical quantitates of the first order. The Runge–Kutta fourth order algorithm, in conjunction with the shooting strategy, is used to provide numerical results for motion and concentration profiles. The impacts of numerous factors on speed and concentration domains, such as the Hartman number, Schmidt number, and chemical reaction parameter, are depicted in graphs. The influence of Deborah numbers and Hartmann numbers on velocities components is the same. As the magnitude of the Hartmann number raised, boundary-layer thickness decreases. The concentration fields shrink as Sc increases and fall for the destructive reaction factor. The surface mass transfer decreases as Hartmann’s number is increased. The heat-transfer rate statistics data are very thoroughly recorded and analysed. The novelty of the present work is to investigate the Jeffery fluid in the presence of a magnetic field along with a chemical reaction over a nonlinear stretching sheet, which has not been investigated yet, so for limiting cases the present work is compared with the published work and good agreement is found.

Numerical study on the effect of fin length variation on the thermal performance of a bus duct conductor

This article presents a finite volume-based simulation study on the effect of fin length variation on the thermal performance of a bus duct conductor. The study was conducted by developing a numerical model using ANSYS FLUENT. IEC 60439-1 and IEC 60439-2 standards were employed as a guideline to conduct the experimental setup. It was found that increasing the fin length increases the total heat transfer rate. This is due to an increase in the surface area exposed to the fluid and a decrease in the thermal boundary layer thickness. However, it was observed that longer fin lengths contributed to greater frictional forces on the fluid that resulted in a drop in convective heat transfer coefficient. The current numerical study is expected to provide a better understanding of the effect of fin length on the thermal performance of a bus duct conductor.

Influence of the Filler Particles' Surface Morphology on the Polyurethane Matrix's Structure Formation in the Composite.

This article presents the surface morphology effect of silicon carbide (SiC) particles on the polyurethane binder’s structure formation in a dispersed-filled composite. The difference in the morphology and surface relief of filler particles was ensured by the implementation of plasma chemical modification. As a result of this modification, the filler consisted of core-shell particles characterized by a SiC core and a carbon shell (SiC@C), as well as a carbon shell decorated with silicon nanoparticles (SiC@C/SiNP) or nanos (SiC@C/SiNW). The study of the relaxation properties of polyurethane composites has shown that the strongest limiting effect on the molecular mobility of boundary layer’s chain segments is exerted by a highly developed surface with a complex relief of SiC@C/SiNP and SiC@C/SiNW particles. An empirical method was proposed to find the polymer fractions spent on the formation of the boundary, transition and bulk layers of the polymer matrix in the composite. It was shown that the morphology of the filler particles’ surface does not affect the dependence of the boundary layer thickness on the filler’s volume fraction. However, with an increase in the degree of surface development, the boundary layer thickness decreases.

Novel MIL101(Fe) impregnated poly(vinylidene fluoride-co-hexafluoropropylene) mixed matrix membranes for dye removal from textile industry wastewater

In this work, the potential of direct contact membrane distillation (DCMD) technology using novel MIL101(Fe) impregnated poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) mixed matrix membranes has been explored for dye removal from the textile industry wastewater. The influence of MIL101(Fe) impregnation on membrane performance was investigated by various morphological (SEM, AFM) and spectral techniques (XRD, FT-IR) along with transmembrane flux and dye rejection efficiency. Membrane performance over the range of feed temperature and the flow rate has also been explored for its applicability and suitability. The permeate flux grows exponentially with the feed temperature, whereas the dye rejection decreased with increased feed temperature. A decrease in boundary layer thickness at the membrane surface resulted in a linear increase in permeate flux with flow rate. The rejection was negligibly affected by the increase in flow rate. Among the fabricated membranes, M-M(0.5) (20% PVDF-HFP/0.5% MIL101(Fe)) membrane was adjudged the most suitable. Response surface methodology was used to investigate the influence of feed temperature and flow rate on permeate flux and dye rejection to optimize membrane performance. The optimized process parameters obtained were feed temperature: 353 K, flow rate: 40 l h−1. For these optimized input process parameters, the predicted responses were permeate flux: 6.75 l m−2 h−1 and dye rejection: 98.14%. Using the optimized parameters obtained from the RSM study, 24 h long run DCMD experiment was done to study membrane fouling on membranes using SEM and FT-IR analysis. The fabricated membranes showed great potential to treat real textile industry wastewater.

Theoretical analysis of Brownian and thermophoresis motion effects for Newtonian fluid flow over nonlinear stretching cylinder

The Brownian and thermophoresis motion effects for the Newtonain nanofluid over a nonlinear stretching cylinder is taken into account in this analysis. The stagnation flow with chemical reaction effects analyzed for Newtonain nanofluid model. Flow is taken along the axial direction and developed the boundary layer approximation. Under the flow assumptions, mathematical model developed through Navier Stoke equations by means of boundary layer approximations. The developed model in terms of partial differential equations achieved by using the boundary layer approximations on the Navier Stoke equations. Furthermore, partial differential equations transformed into ordinary differential equations after applying the similarity variable. The achieved ordinary differential equations are solved through numerical procedure namely bvp4c technique. The results are achieved after solving the differential equations and involing physical parameters effects are presented in term of tabular as well as graphicals. By increasing prandtl number as well as the thermal boundary layer thickness decreases. Effect of Re which improve the velocity field and decrease the temperature and concentration profile.

Impact of Hall Current and Nonlinear Thermal Radiation on Jeffrey Nanofluid Flow in Rotating Frame

This research article deals with the nonlinear thermally radiated influences on non-Newtonian nanofluid considering Jeffrey fluid in a rotating system. The governing equations of the nanofluid have been transformed to a set of differential nonlinear equations, using suitable similarity variables. The Homotopy Analysis Method (HAM) and Runge–Kutta Method of order 4 (RK Method of order 4) are used for the solution of the modeled problem. The variation of the skin friction, Nusselt number, Sherwood number, and their impacts on the velocity distribution, temperature distribution, and concentration distribution have been examined. The influence of the Hall effect, rotation, Brownian motion, porosity, and thermophoresis analysis are also investigated. Moreover, for comprehension of the physical presentation of the embedded parameters, Deborah numberβ, viscosity parameterR, rotation parameterKr, Brownian motion parameterNb, porosity parameterγ, magnetic parameterM, Prandtl numberPr, thermophoretic parameterNt, and Schmidt numberSchave been plotted and deliberated graphically. For large values of Brownian parameter, the kinetic energy increases, which in turn increases the temperature distribution, while the thermal boundary layer thickness decreases by increasing the radiation parameter, and the Hall parameter increases the motion of the fluid in horizontal direction. Also, the mass flux has been observed as a decreasing function at the lower stretching plate.

Cooling capacity of magnetic nanofluid in presence of magnetic field based on first and second laws of thermodynamics analysis

ABSTRACT In this numerical study, the cooling capacity of water/Cu magnetic nanofluids in a horizontal duct exposed to a magnetic field has been investigated. Both the first and second laws of thermodynamics analysis are conducted. All simulations have been performed for the volume fraction of 5%, Reynolds number (Re) of 100, and the Hartmann numbers (Ha) of 0, 20, 50, and 80. Temperature, velocity profiles, Nusselt number (Nu), Lorentz force (F), and thermal, frictional, and magnetic irreversibility have been studied by changing Ha. The received results indicate that as the Ha increases, the hydrodynamic boundary layer thickness decreases, while the length of the hydrodynamic entrance length increases. In addition, as the Ha increases in the range of 0 to 80, the local Nu number increases by about 7.5%, and the local wall temperature drops to 2.7%. The second law of thermodynamic analysis showed that as the Ha increases, the frictional irreversibility augments, while the thermal irreversibility decreases. Finally, the order of thermal irreversibility is larger than that of frictional and magnetic irreversibility.

Effects of thermal radiation on Eyring–Powell fluid flow and heat transfer over a power-law stretching permeable surface

The main objective of this paper is to investigate the effects of thermal radiation on Eyring–Powell fluid flowing over a power-law stretching sheet in presence of suction/blowing. Similarity transformations are used to find the self-similar form of the governing equations. It is established that for a particular value of power-law stretching velocity self-similar solutions exist for the problem. Shooting technique is applied for solving numerically the reduced ordinary differential equations. The effects of fluid parameters, suction/blowing parameter on velocity, skin friction co-efficient, temperature, and wall temperature gradient are analyzed and presented through tables and graphs as far as practicable. The effect of radiation parameter on wall temperature gradient is presented graphically. Velocity decreases with the increasing values of one of the fluid parameter and increases with increasing values of the other fluid parameter. Velocity and momentum boundary layer thickness decrease with the increasing values of suction/blowing parameter. For one fluid parameter, the absolute values of skin friction co-efficient decrease but the absolute values of temperature gradient at the wall increase. On the other hand, reverse trend is noted for other fluid parameter. The values of wall temperature gradient decrease with increasing Prandtl number and radiation parameter. Dimensionless temperature and thermal boundary layer thickness decrease with rise in Prandtl number, radiation parameter, and suction/blowing parameter.

Numerical Solution of MHD Nanofluid Over a Stretching Surface with Chemical Reaction and Viscous Dissipation

The main objective of this paper is to focus on a numerical study of chemical reaction and viscous dissipation effects on the steady state boundary layer flow of MHD nanofluid past the horizontally stretching sheet with the existence of nanoparticles. A proper similarity transformation is utilized to convert the boundary layer equations into the nonlinear and coupled ordinary differential equations. These ODEs are sorted out numerically by applying the shooting mechanism. Graphical representations are also included to explain the effect of evolving parameters against the above-mentioned distributions. Significance of different physical parameters on dimensionless velocity, temperature and concentration are elaborated through graphs and tables. For increasing values of Eckert number, the temperature profile increases whereas the chemical reaction parameter increases, the boundary layer thickness decreases.
 Chemical Engineering Research Bulletin 21(2019) 36-45

Experimental investigation on the heat transfer performance of MHTHS using ethylene glycol-based nanofluids

Experimental investigation on the heat transfer characteristics of the nanofluids passing through mini hexagonal tube heat sink (MHTHS) was accomplished. Al2O3–EG, CuO–EG, and SiO2–EG nanofluids with volume fraction ranging from 0.01 to 0.04% were chosen in the present study. The dispersion of nanoparticles in ethylene glycol (EG) was used as the working fluids. The volume flow rate of nanofluids flow through the hexagonal tube side was varied from 15 to 50 L h−1, and the hot deionized water in mini passage side was kept constant at a volume flow rate of 30 L h−1. The heat transfer characteristics of nanofluids were studied with the concentration of nanoparticles in base fluid and effect of Reynolds number. The heat transfer coefficient of MHTHS was measured under fully developed laminar and turbulent flow conditions. Based on the experimental data, it was observed that thermal conductivity, heat transfer coefficient, and Nusselt number of CuO–EG nanofluid were found to be higher when compared to other two nanofluids. The thermal conductivity of nanofluids was enhanced with an increase in concentration of nanoparticles in EG. The enhancement in heat transfer coefficient of nanofluid was achieved at higher turbulence in turbulent flow. It was due to stable dispersion of nanoparticles in EG. Therefore, the enhancement in heat transfer coefficient was found to be 36%, 32%, and 22% for CuO–EG, Al2O3–EG, and SiO2–EG nanofluid, respectively, at the concentration of 0.04 vol%. At higher Reynolds number, the agglomeration of nanoparticles decreases. Hence, it caused a decrease in boundary layer thickness which leads to an increase in the heat transfer-enhanced Nusselt number. The friction factor of SiO2–EG nanofluid was found to be lower in turbulent flow regime, and furthermore, it had no substantial effect in laminar flow regime.

The Impact of Nanoparticles Due to Applied Magnetic Dipole in Micropolar Fluid Flow Using the Finite Element Method

The present work examines the effect of different magnetic nanoparticles and the heat transfer phenomena over the stretching sheet with thermal stratification and slips effect. The mixture of water (H 2 O) and ethylene glycol (C 2 H 6 O 2 ) is used as base fluid whereas the paramagnetic, diamagnetic, and ferromagnetic ferrites are taken as nanoparticles. In the presence of ferrite nanoparticles, the magnetic dipole has a significant effect in controlling the rate of heat transfer and the thermal boundary layers. By using suitable similarity transformations, the system of partial differential equations is transformed into nonlinear ordinary differential equations. The numerical solution of resulting equations is found out by using the variational finite element method. The effect of numerous emerging parameters on velocity, temperature, and micro-rotation velocity are represented graphically and analyzed numerically. It has been noticed that comparatively the diamagnetic ferrites have gained maximum thermal conductivity relative to the other nanoparticles. It was also observed that the thermal conduction of nanoparticles increases with the variation of volume fraction. Moreover, with increasing values of thermal stratification the thermal boundary layer thickness decreases and the heat transfer rate increases at the surface. Furthermore, the validation of code and the accuracy of the numerical technique has been confirmed by the assessment of current results with earlier studies.