J. Rajakumar, P. Saikrishnan and A. Chamkha
The purpose of this paper is to consider axisymmetric mixed convection flow of water over a sphere with variable viscosity and Prandtl number and an applied magnetic field.
Abstract
Purpose
The purpose of this paper is to consider axisymmetric mixed convection flow of water over a sphere with variable viscosity and Prandtl number and an applied magnetic field.
Design/methodology/approach
The non-similar solutions have been obtained from the origin of the streamwise co-ordinate to the point of zero skin friction using quasilinearization technique with an implicit finite-difference scheme.
Findings
The effect of M is not notable on the temperature and heat transfer coefficient when λ is large. The skin friction coefficient and velocity profile are enhance with the increase of MHD parameter M when λ is small. Viscous dissipation has no significant on the skin friction coefficient under MHD effect. For M=1, the movement of the slot or slot suction or slot injection do not cause any effect on flow separation. The slot suction and the movement of the slot in downstream direction delay the point of zero skin friction for M=0.
Originality/value
The present results are original and new for water boundary-layer flow over sphere in mixed convection flow with MHD effect and non-uniform mass transfer. So this study would be useful in analysing the skin friction and heat transfer coefficient on sphere of mixed convection flow of water boundary layer with MHD effect.
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G. Revathi, P. Saikrishnan and A. Chamkha
The purpose of this paper is to make an analysis to study the non‐similar solution for unsteady water boundary layer flow over sphere with the influence of temperature‐dependent…
Abstract
Purpose
The purpose of this paper is to make an analysis to study the non‐similar solution for unsteady water boundary layer flow over sphere with the influence of temperature‐dependent viscosity, Prandtl number, non‐uniform surface mass transfer and heat transfer.
Design/methodology/approach
The governing quasi‐linear partial differential equations have been solved numerically using an implicit finite difference scheme along with a quasi‐linearization technique. Non‐similar solutions have been obtained from the starting point of the stream‐wise coordinate to the point where the skin friction value vanishes.
Findings
It is observed that non‐uniform suction causes the point of vanishing skin friction to move downstream. The slot injection causes the vanishing skin friction to move upstream.
Originality/value
The effect of unsteadiness is more significant on the skin friction as compared to the heat transfer.
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The purpose of this paper is to study the effect of non‐uniform double slot suction (injection) into a steady laminar boundary layer flow over a yawed cylinder when fluid…
Abstract
Purpose
The purpose of this paper is to study the effect of non‐uniform double slot suction (injection) into a steady laminar boundary layer flow over a yawed cylinder when fluid properties such as viscosity and Prandtl number are inverse linear functions of temperature. Non‐similar solutions have been obtained from the starting point of the streamwise co‐ordinate to the exact point of separation.
Design/methodology/approach
The governing equations are tackled by the implicit finite difference scheme in combination with the quasi‐linearization technique. Quasi‐linear technique can be viewed as a generalization of the Newton‐Raphson approximation technique in functional space. An iterative sequence of linear equations is carefully constructed to approximate the nonlinear equations for achieving quadratic convergence and monotonicity. The quadratic convergence and monotonicity are unique characteristics of the quasilinear implicit finite difference scheme, which makes this scheme superior to built‐in iteration of upwind or finite amplitude techniques.
Findings
The results indicate that the separation can be delayed by non‐uniform double slot suction and also by moving the slot downstream. However, the effect of non‐uniform double slot injection is just the opposite. Yaw angle has very little affect on the location of the point of separation.
Originality/value
This analysis is useful in understanding many boundary layer problems of practical importance for undersea applications, for example, in suppressing recirculating bubbles and controlling transition and/or separation of the boundary layer over submerged bodies.
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Iyyappan G. and Abhishek Kumar Singh
The purpose of this paper is to analyse the force convection laminar boundary layer flow on irregular boundary in diverging channel with the presence of magnetic field effects…
Abstract
Purpose
The purpose of this paper is to analyse the force convection laminar boundary layer flow on irregular boundary in diverging channel with the presence of magnetic field effects. Effects of various fluid parameters such as suction/injection, viscous dissipation, magnetic parameter and heat source/sink on velocity and temperature profiles are numerically analyzed. Moreover, numerically investigated on skin-friction and heat transfer coefficients when suction/injection occur.
Design/methodology/approach
The governing coupled partial differential equations are transformed to dimensionless form using non-similarity transformations. The non-dimensional partial differential equations are linearized by quasi-linearization technique and solved by varga's algorithm with numerical finite difference scheme on a non-uniform mesh.
Findings
The computation results are presented in terms of temperature, heat transfer and skin friction coefficients; these are useful for determining surface heat requirements. It was found that, in finite difference scheme for non-uniform mesh with quasi-linearization technique method gives smoothness of solution compared to finite difference scheme for uniform mesh, and this evidence is graphically represented in Figure 2.
Originality/value
The impacts of viscous dissipation (Ec) and magnetic parameter (Ha) on temperature profiles, skin friction and heat transfer are analyzed, which determine the heat generation/absorption to ensure the MHD flow of the laminar boundary layer on irregular boundary over a diverging channel.
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Abhishek Kumar Singh, A.K. Singh and S. Roy
The purpose of the present study is to analyze the mixed convection water boundary layer flows over moving vertical plate with variable viscosity and Prandtl number. The…
Abstract
Purpose
The purpose of the present study is to analyze the mixed convection water boundary layer flows over moving vertical plate with variable viscosity and Prandtl number. The non-linear partial differential equation governing the flow and thermal fields are presented in non-dimensional form by using appropriate transformation. The quasi-linearization technique in combination with implicit finite difference scheme has been adopted to solve the nonlinear-coupled partial differential equation. The numerical results are displayed graphically to illustrate the influence of various non-dimensional physical parameters on velocity and temperature. Further, the numerical results for local skin-friction coefficient and local Nusselt number are also reported. The present findings are compared with previously reported results, and these comparisons are found to be in excellent agreement.
Design/methodology/approach
The nonlinear partial differential equations governing the flow and thermal fields have been solved numerically using the implicit finite difference scheme in combination with the quasi-linearization technique. The numerical results are presented in terms of skin friction and heat transfer rate which are useful in determining the surface heat requirements for stabilizing the laminar boundary layer flow over a moving plate in water.
Findings
The effect of the ratio of free-stream velocity to the composite reference velocity is significant on the velocity profile. Near the wall region, as ratio of free stream velocity to composite reference velocity increases form 0.1 to 0.5, the velocity overshoot gets enhanced from 3 per cent to 41 per cent. The influence of buoyancy parameter and ration of free stream velocity to composite reference velocity on temperature profile is comparatively less than on velocity profiles. The increase in the skin friction coefficient is dependent on the increase in the value of ratio of free stream velocity to composite reference velocity if the buoyancy parameter λ is fixed and vice versa and increases in ΔT results in a decrease in N and Pr.
Originality/value
The present investigation is to deal with the solution of steady laminar water boundary layer flows over a moving plate with temperature-dependent viscosity and Prandtl number applicable for water using practical data. The fluid considered here is water, as it is one of the most common working fluids found in engineering applications.
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Prabhugouda Mallanagouda Patil, Shashikant A. and Ebrahim Momoniat
This paper aims to investigate the unsteady mixed convection along an exponentially stretching surface in presence of transverse magnetic field applied at the wall and the…
Abstract
Purpose
This paper aims to investigate the unsteady mixed convection along an exponentially stretching surface in presence of transverse magnetic field applied at the wall and the opposing buoyancy flow.
Design/methodology/approach
The dimensional partial differential equations governing the flow field are transformed to non-dimensional coupled partial differential equations with the aid of suitable non-similar transformations. The resulting equations are then solved by the coalition of quasilinearization technique and the finite difference method.
Findings
Effects of volumetric heat source/sink, suction/blowing and other dimensionless parameters on velocity and temperature profiles are examined numerically. This investigation reveals that in presence of opposing buoyancy flow, the suction and volumetric heat source enhances the skin-friction coefficient, while the rise in the MHD increases the momentum boundary layer.
Originality/value
To the best of the authors’ knowledge, no such investigation has been carried out in the literature.
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P. Saikrishnan, Satyajit Roy, H.S. Takhar and R. Ravindran
The purpose of this paper is to study the influence of thermally stratified medium on a free convection flow from a sphere, which is rotating about the vertical axis, immersed in…
Abstract
Purpose
The purpose of this paper is to study the influence of thermally stratified medium on a free convection flow from a sphere, which is rotating about the vertical axis, immersed in a stably thermally stratified medium.
Design/methodology/approach
An implicit finite‐difference scheme in combination with the quasi‐linearization technique is applied to obtain the steady state non‐similar solutions of the governing boundary layer equations for flow and temperature fields.
Findings
The numerical results indicate that the heat transfer rate at the wall decreases significantly with an increasing thermal stratification parameter, but its effect on the skin friction coefficients is rather minimum. In fact, the presence of thermal stratification of the medium influences the heat transfer at wall to be in opposite direction, that is, from fluids to the wall above a certain height. The heat transfer rate increases but the skin frictions decrease with the increase of Prandtl number. In particular, the effect of buoyancy force is much more sensitive for low Prandtl number fluids (Pr = 0.7, air) than that of high Prandtl number fluids (Pr = 7, water). Also the skin friction in rotating direction is less sensitive to the buoyancy force as the buoyancy force acts in the streamwise direction for the present study of thermally stratified medium.
Research limitations/implications
The ambient temperature T∞∞ is assumed to increase linearly with height $h$. The viscous dissipation term, which is usually small for natural convection flows, has been neglected in the energy equation. The flow is assumed to be axi‐symmetric. The Boussinesq approximation is invoked for the fluid properties to relate density changes to temperature changes, and to couple in this way the temperature field to the flow field.
Practical implications
Free convection in a thermally stratified medium occurs in many environmental processes with temperature stratification, and in industrial applications within a closed chamber with heated walls. Also, free convections associated with heat rejection systems for long‐duration deep ocean powder modules where ocean environment is stratified are examples of such type.
Originality/value
The research presented in this paper investigates the free convection flow on a sphere, which is rotating with a constant angular velocity along its vertical axis in a stably thermally stratified fluid.
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Satya Prakash Singh, Gautam Biswas and Perumal Nithiarasu
The purpose of this paper is to investigate the influence of forced, in-line oscillation of a circular cylinder on an incoming incompressible flow field at different Reynolds…
Abstract
Purpose
The purpose of this paper is to investigate the influence of forced, in-line oscillation of a circular cylinder on an incoming incompressible flow field at different Reynolds numbers.
Design/methodology/approach
A space-time finite element approach is employed to model the flow around an oscillating cylinder.
Findings
The results show that two (2S), four (2P, two pair) and three vortices (P+S, one pair and one single) are shed in each cycle. In addition, a 2P o mode is also observed, which is similar to the 2P mode but the vortices of the 2P o mode differ in strength. The 2P mode of vortex shedding is observed along the entire wake of the flow field and 2P o mode in the far wake. In some cases, the vortex street is transformed as it travels towards the exit to produce new patterns. One such pattern is observed for the first time in the present work, which is referred to as 2P o* mode. The drag and lift coefficients observed are perfectly periodic at a Reynolds number of 200 and they reach a chaotic pattern as the Reynolds number is increased to a value of 350.
Originality/value
Originality of the paper lies in the observation of 2P vortex shedding mode or its variants in the downstream of the cylinder.
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Baskara Sethupathi P. and Chandradass J.
This study aims to compare the influence of different solid lubricants on the friction stability of a non-asbestos disc brake pad.
Abstract
Purpose
This study aims to compare the influence of different solid lubricants on the friction stability of a non-asbestos disc brake pad.
Design/methodology/approach
Three brake pads were developed using three lubricants, namely, non-asbestos brake pad with sulfide mix (NASM), non-asbestos brake pad with bismuth sulfide (NABS) and non-asbestos brake pad with molybdenum disulfide (NAMO). Sulfide mix was indigenously developed by physically mixing friction modifiers, alkaline earth chemicals and various metallic sulfides homogeneously dispersed in graphite medium. The physical, chemical, mechanical and thermal properties of brake pads were characterized as per industrial standards. The tribological performances were studied using the Chase testing machine as SAE-J661-2012. The worn surface of the pads was studied using scanning electron microscope to analyze the dominating wear mechanism.
Findings
NASM was excellent in fade as well as wear resistance. NABS was better from a wear point of view, but fade resistance was moderate despite its higher cost. NAMO fared average in fade and wear despite its excellent dry lubricating properties. NASM was excellent in terms of fade as well as wear resistance.
Originality/value
Among the selected metal sulfides, the indigenously developed sulfide mix was better than the other two sulfides, which indicates that the synergetic effect of metal sulfides was always preferable to the individual sulfides.
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P.M. Patil, S. Roy and Ali J. Chamkha
The purpose of this paper is to consider steady two‐dimensional mixed convection flow along a vertical semi‐infinite power‐law stretching sheet. The velocity and temperature of…
Abstract
Purpose
The purpose of this paper is to consider steady two‐dimensional mixed convection flow along a vertical semi‐infinite power‐law stretching sheet. The velocity and temperature of the sheet are assumed to vary in a power‐law form.
Design/methodology/approach
The problem is formulated in terms of non‐similar equations. These equations are solved numerically by an efficient implicit, iterative, finite‐difference method in combination with a quasi‐linearization technique.
Findings
It was found that the skin‐friction coefficient increased with the ratio of free‐stream velocity to the composite reference velocity and the buoyancy parameter while it decreased with exponent parameter. The heat transfer rate increased with the Prandtl number, buoyancy parameter and the exponent parameter.
Practical implications
A very useful source of information for researchers on the subject of convective flow over stretching sheets.
Originality/value
This paper illustrates mixed convective flow over a power‐law stretched surface with variable wall temperature.