Effect Of Uniform Suction Research Articles

Heat generation/absorption and velocity slip effects on unsteady axisymmetric flow of Williamson magneto-nanofluid

Engineers and researchers in the field of heat transfer are in search of new techniques to optimize the performance of energy devices through heat transfer enhancement. For that reason, the flow analysis involving nanoparticles is assumed to be one of the most important techniques for enhancing heat transfer systems. Being a two-component system, different numerical approaches are available to model the thermo-fluids behavior of nanofluids. The current study describes the investigation of Buongiorno model for evaluation of transient flow and heat transfer of Williamson nanofluids under the impacts of velocity slip and magnetic field. In addition, the effects of heat generation/absorption and convective heat transfer have been employed in this analysis. The Boussinesq-approximations are implemented to obtain the governing conservation equations for nanofluids transport phenomenon. The leading equations of the modeled physical problem have been solved using a MATLAB code, based on Nachtsheim–Swigert shooting iteration scheme. The novelty of the current investigation is the existence of multiple solutions for the nanofluids flow past a radially shrinking surface by considering the effects of uniform suction at the wall. In this review, it is seen that the investigated physical parameters affect remarkably on the nanofluid stream function, temperature and nanoparticles concentration. The skin friction, local Nusselt number and the local Sherwood number and some samples of velocity, temperature and nanoparticle concentration profiles are discussed and presented with the help of graphs. From this study, it is observed that the existence range of dual solutions is significantly raised by the higher Weissenberg number.

Effect of wall suction on rotating disk absolute instability

This research investigates the effect of uniform suction on the absolute instability of Type I cross-flow modes in the boundary layer on a rotating disk. Specifically, it is designed to investigate whether wall suction would transform the absolute instability into a global mode, as first postulated in the numerical simulations of Davies & Carpenter (J. Fluid Mech., vol. 486, 2003, pp. 287–329). The disk is designed so that with a suction parameter of $0.2$, the radial location of the absolute instability critical Reynolds number, $Re_{c_{A}}=650$, occurs on the disk. Wall suction is applied from $Re=317$ to 696.5. The design for wall suction follows that of Gregory & Walker (J. Fluid Mech., 1960, pp. 225–234) where an array of holes through the disk communicate between the measurement side of the disk and the underside of the disk which is inside of an enclosure that is maintained at a slight vacuum. The enclosure pressure is adjustable so that a range of suction or blowing parameters can be investigated. The holes in the measurement surface are covered by a compressed wire porous mesh to aid in uniformizing the suction on the measurement surface of the disk. The mesh is covered by a thin porous high-density polyethylene sheet featuring a $20~{\rm\mu}\text{m}$ pore size which provides a smooth finely porous surface. A companion numerical simulation is performed to investigate the effect that the size and vacuum pressure of the underside enclosure have on the uniformity of the measurement surface suction. Temporal disturbances are introduced using the method of Othman & Corke (J. Fluid Mech., 2006, pp. 63–94). The results document the evolution of disturbance wavepackets in space and time. These show a temporal growth of the wavepackets as the location of the absolute instability is approached which is in strong contrast to the temporal evolution without suction observed by Othman and Corke. The results appear to support the effect of wall suction on the absolute instability postulated by Thomas (PhD thesis, 2007, Cardiff University, UK) and Thomas & Davies (J. Fluid Mech., vol. 663, 2010, pp. 401–433).

Control of fluid flow and heat transfer around a square cylinder by uniform suction and blowing at low Reynolds numbers

The effects of uniform suction and blowing through the surfaces of a square cylinder on the vortex shedding, wake flow and heat transfer are investigated, Re=70–150, Pr=0.7. All numerical simulations are performed with a finite-volume code based on a collocated grid arrangement. To find the optimum condition, where vortex shedding suppression occurs and the maximum reductions on the forces and their fluctuations provide, three simple cases are examined. In these cases, the influence of the uniform blowing and suction only through the front surface (case I), rear surface (case II) and top/bottom surface (case III) is studied at Re=150. Based on the obtained advantages of these simple cases, different combinations of the suction and blowing on the cylinder sides are considered and an optimum case is introduced. In this case, suction is applied on the top and bottom surfaces and blowing is employed on the front and rear faces. The effect of the Reynolds number on the results for the optimum configuration is also investigated (Re=70, 100, 150). This study shows that the lift and drag fluctuations for the optimum configuration decay and the maximum reduction on the drag force are 61%, 67% and 72% for Re=70, 100, 150, respectively. An optimum case with respect to heat transfer is also introduced where suction is applied through all surfaces.

Effect of uniform suction on nanofluid flow and heat transfer over a cylinder

The aim of the present paper is to study the nanofluid flow and heat transfer over a stretching porous cylinder. The effective thermal conductivity and viscosity of the nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In KKL model, the effect of Brownian motion on the effective thermal conductivity is considered. The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions using similarity transformation, which is then solved numerically by the fourth-order Runge–Kutta integration scheme featuring a shooting technique. Numerical results for flow and heat transfer characteristics are obtained for various values of the nanoparticle volume fraction, suction parameter, Reynolds number and different kinds of nanofluids. Results show that inclusion of a nanoparticle into the base fluid of this problem is capable to change the flow pattern. It is found that Nusselt number is an increasing function of nanoparticle volume fraction, suction parameter and Reynolds number.

THE STUDY OF HEAT AND MASS TRANSFER IN A VISCO ELASTIC FLUID DUE TO A CONTINUOUS STRETCHING SURFACE USING HOMOTOPY ANALYSIS METHOD

In this paper, an approximate analytical solution is derived for the flow velocity and temperature due to the laminar, two-dimensional flow of non-Newtonian incompressible visco elastic fluid due to a continuous stretching surface. The surface is stretched with a velocity proportional to the distance $x$ along the surface. The surface is assumed to have either power-law heat flux or power-law temperature distribution. The presence of source/sink and the effect of uniform suction and injection on the flow are considered for analysis. An approximate analytical solution has been obtained using Homotopy Analysis Method(HAM) for various values of visco elastic parameter, suction and injection rates. Optimal values of the convergence control parameters are computed for the flow variables. It was found that the computational time required for averaged residual error calculation is very very small compared to the computation time of exact squared residual errors. The effect of mass transfer parameter, visco elastic parameter, source/sink parameter and the power law index on flow variables such as velocity, temperature profiles, shear stress, heat and mass transfer rates are discussed.

Boundary layer flow over a moving surface in a nanofluid with suction or injection

An analysis is performed to study the heat transfer characteristics of steady two-dimensional boundary layer flow past a moving permeable flat plate in a nanofluid. The effects of uniform suction and injection on the flow field and heat transfer characteristics are numerically studied by using an implicit finite difference method. It is found that dual solutions exist when the plate and the free stream move in the opposite directions. The results indicate that suction delays the boundary layer separation, while injection accelerates it.

Mixed Convection Boundary Layer Flow over a Permeable Vertical Flat Plate Embedded in an Anisotropic Porous Medium

An analysis is performed to study the heat transfer characteristics of steady mixed convection flow over a permeable vertical flat plate embedded in an anisotropic fluid-saturated porous medium. The effects of uniform suction and injection on the flow field and heat transfer characteristics are numerically studied by employing an implicit finite difference Keller-box method. It is found that dual solutions exist for both assisting and opposing flows. The results indicate that suction delays the boundary layer separation, while injection accelerates it.

Asymptotic stability of linearly evolving non-stationary modes in a uniform hydromagnetic field over a rotating-disk flow with suction and injection

In this paper the linear stability properties of the magnetohydrodynamic flow of an incompressible, viscous and electrically conducting fluid are investigated for the boundary-layer due to an infinite permeable rotating-disk. The fluid is subjected to an external magnetic field perpendicular to the disk. The interest lies also in finding out the effects of uniform suction or injection. In place of the traditional linear stability method, a theoretical approach is adopted here based on the high-Reynolds-number triple-deck theory. It is demonstrated that the nonstationary perturbations evolve in accordance with an eigenrelation analytically obtained.

Effects of uniform suction and surface tension on laminar filmwise condensation on a horizontal elliptical tube in a porous medium

This study performs a theoretical investigation into the problem of steady filmwise condensation flow over the external surface of a horizontal elliptical tube embedded in a porous medium with suction at the tube surface. The combined effects of the surface tension force and the gravitational force in driving the flow of the liquid film within the porous medium are modeled using Darcy's law. An effective suction function, f, is introduced to model the effect of the suction force at the wall on the thickness of the condensate film. The theoretical results presented in this study show that the heat transfer performance can be enhanced by applying a suction effect at the wall. Furthermore, it is shown that the surface tension force has a negligible effect on the mean Nusselt number.

Analytic study of magnetohydrodynamic flow and boundary layer control over a wedge

A genuine variational principle developed by Gyarmati, in the field of thermodynamics of irreversible processes unifying the theoretical requirements of technical, environmental and biological sciences is employed to study the effects of uniform suction and injection on MHD flow adjacent to an isothermal wedge with pressure gradient in the presence of a transverse magnetic field. The velocity distribution inside the boundary layer has been considered as a simple polynomial function and the variational principle is formulated. The Euler-Lagrange equation is reduced to a simple polynomial equation in terms of momentum boundary layer thickness. The velocity profiles, displacement thickness and the coefficient of skin friction are calculated for various values of wedge angle parameter m, magnetic parameter 5m and suction/injection parameter H. The present results are compared with known available results and the comparison is found to be satisfactory. The present study establishes high accuracy of results obtained by this variational technique.

The Blasius, Sakiadis and Blasius Sakiadis flow with uniform suction: a unified approach

A theoretical study of the effect of uniform suction on the classical Blasius and Sakiadis flow is presented in this note. The results are obtained with the numerical simulation of the governing equations. Except of the numerical solution of the boundary layer equations we produced some simple analytical solutions for the asymptotic suction state. Velocity and temperature profiles are presented for different values of the suction parameter ξ. It is found that the velocity asymptotic state is reached at ξc≈2 for all cases, that is, Blasius flow, Sakiadis flow and combined Blasius?Sakiadis flow. However, for the temperature asymptotic state no universal suction parameter exists and ξc depends on the Prandtl number.

Modelling and Analytical Solution to Heat Transfer and Boundary Layer Flow with Suction and Injection

A genuine variational principle developed by Gyarmati in the field of thermodynamics of irreversible processes unifying the theoretical requirements of technical, environmental, and biological sciences is employed to study the effects of uniform suction and injection in the heat transfer and boundary layer flow with power function main stream velocity and surface temperature variations, over a wedge. The velocity and temperature distributions inside the boundary layer are considered as simple polynomial functions and the variational principle is formulated. The Euler–Lagrange equations are reduced to simple polynomial equations in terms of boundary layer thicknesses. The values of skin friction and heat transfer are calculated for any given values of Prandtl number Pr , wedge angle parameter m , wall temperature exponent n , and suction/injection parameter H . The obtained analytic results are compared with known numerical solutions and the comparison establishes the fact that the accuracy is remarkable.

Hydromagnetic rotating flow of a fourth‐order fluid past a porous plate

AbstractThe rotating flow in the presence of a magnetic field is a problem belonging to hydromagnetics and deserves to be more widely studied than it has been to date. In the non‐linear regime the literature is scarce. We develop the governing equations for the unsteady hydromagnetic rotating flow of a fourth‐order fluid past a porous plate. The steady flow is governed by a boundary value problem in which the order of differential equations is more than the number of available boundary conditions. It is shown that by augmenting the boundary conditions based on asymptotic structures at infinity it is possible to obtain numerical solutions of the nonlinear hydromagnetic equations. Effects of uniform suction or blowing past the porous plate, exerted magnetic field and rotation on the flow phenomena, especially on the boundary layer structure near the plate, are numerically analysed and discussed. The flow behaviours of the Newtonian fluid and second‐, third‐ and fourth‐order non‐Newtonian fluids are compared for the special flow problem, respectively. Copyright © 2004 John Wiley & Sons, Ltd.

Effect of uniform suction on laminar filmwise condensation on a finite-size horizontal flat surface in a porous medium

The theoretical analysis of filmwise condensation outside a finite-size horizontal flat surface embedded in a porous medium filled with a dry saturated vapor has been solved by a boundary layer treatment. The Newton–Raphson scheme was employed to solve the finite-size horizontal flat plate in porous medium. Results turns out that the average Nusselt number for condensation heat transfer is expressed in terms of Darcy number, Jakob number, film liquid Prandtl number, Darcy-modified Rayleigh number and the parameter of suction, as well as are given for the condensate layer thickness profiles.

ON THE EFFECTIVENESS OF UNIFORM SUCTION-INJECTION ON THE UNSTEADY FLOW DUE TO A ROTATING DISK WITH HEAT TRANSFER

The unsteady flow of an incompressible viscous fluid above an infinite rotating porous disk is studied with heat transfer. The effect of uniform suction or injection through the surface of the disk on the velocity and temperature distributions as well as the heat transfer is considered. Numerical solutions of the nonlinear equations which govern the hydrodynamics and energy transfer are obtained

Unsteady flow induced by variable suction on a porous disk rotating eccentrically with a fluid at infinity

We study the effect of variable suction or blowing on the flow of an incompressible viscous fluid due to noncoaxial rotations of a porous disk and a fluid at infinity. The inquiries are made about the components of fluid velocity and the shear stress at the disk. It is found that the effect of uniform suction or blowing on the flow is enhanced in the presence of variable suction or blowing.

Laminar mixed convection over horizontal flat plate embedded in a non-Darcian porous medium with suction and injection

An analysis is performed to study the heat transfer characteristics of laminar mixed convective boundary layer flow over a semi-infinite horizontal flat plate embedded in porous medium. The effect of uniform suction and injection on the horizontal flat plate with uniform surface temperature is numerically studied by employing an implicit finite difference Keller's box method. Numerical results show that non-Darcian have significant influences on velocity profiles, temperature profiles and heat transfer rates from the horizontal surface. The results indicate that the suction enhances the heat transfer coefficient while injection causes a decrease in heat transfer.

Hydromagnetic flow between rotating eccentric cylinders with suction at the porous walls

The flow of a viscous, incompressible fluid between two eccentric rotating porous cylinders with suction/injection at both the cylinders, for very small clearance ratio is studied. The expressions for various flow characteristics are obtained using per- turbation analysis. Streamlines and pressure plots are shown graphically for various values of flow parameters and discussed. 2000 Mathematics Subject Classification. Primary 76D08. 1. Introduction. In the present investigation we have considered the viscous flow between eccentric porous rotating cylinders. The effect of uniform suction and in- jection is studied on the walls of the cylinders. Several authors have analysed flow through rotating eccentric cylinders for various flow situations. In particular the com- plex hydrodynamical lubrication problem as flow between two rotating eccentric cylin- ders was analysed by Reynolds (10). Wannier (13) presented an exact solution of the Stokes equation for the flow between rotating eccentric cylinders. Here, the pressure distribution reduces to the classical Sommerfeld solution of the Reynolds equation in the limit of small clearance ratio, and provides a correction for curvature effects. Wood (14) has studied the asymptotic expansion at large Reynolds number for steady motion between non-coaxial eccentric rotating cylinders using modified bipolar coor- dinate system. Kamal (6) has considered the effect of the inertial terms on the flow be- tween rotating eccentric cylinders. As no restriction was laid on the clearance ratio, the analysis is somewhat complicated when applied to the lubrication problem. Kulinski and Ostrach (7) also have considered the effect of inertia on the flow in a journal bearing by using a perturbation procedure for small eccentricity. Sood and Elrod (12) have used numerical techniques to solve the full Navier-Stokes equations for the flow between eccentric rotating cylinders but for a clearance ratio of 1.0 only. DiPrima and Stuart (3) have studied the hydrodynamic flow between rotating eccentric cylinders using the modified bipolar coordinate system. They derived the Sommerfeld pressure distribution and associated flow from the Navier-Stokes equation by a straightforward and systematic expansion in the clearance ratio (assumed small). Dintenfass (2) considered the role of cartilage elasticity coupled with the non- newtonian behaviour of synovial fluid to explain the joint lubrication. Dawson (4) suggested the existence of more than one mode of lubrication namely boundary lu- brication, and this idea was supported by McCutchen (9) who concluded that weeping lubrication was not the sum total of joint lubrication but was supplemented with

308 くさび形物体に沿うMHD複合対流境界層に及ぼす吸込み吹出しの影響(流体工学II)

308 くさび形物体に沿うMHD複合対流境界層に及ぼす吸込み吹出しの影響(流体工学II)

Flow of a viscous incompressible fluid of temperature dependent viscosity past a permeable wedge with uniform surface heat flux

The effect of uniform suction on the steady two-dimensional laminar forced flow of a viscous incompressible fluid of temperature dependent viscosity past a wedge with uniform surface heat flux is considered. The governing equations for the flow are obtained by using suitable transformations and are solved by using an implicit finite difference method. Perturbation solutions are also obtained near the leading edge and in the downstream regime. The results are obtained in terms of the local skin friction coefficient and the rate of heat transfer for various values of the pertinent parameters, such as the Prandtl number, Pr, the velocity gradient parameter, m, the local suction parameter, ξ, and the viscosity variation parameter, ɛ. Perturbation solutions are compared with the finite difference solutions and are found to be in excellent agreement. The effect of ξ, m and ɛ on the dimensionless velocity profiles and viscosity distribution are also presented graphically for Pr = 0.7 and 7.0, which are the appropriate values for gases and water respectively.