Nirmal C. Sacheti

Hydromagnetic flow and heat transfer past a continuously moving porous boundary

The effect of magnetic field on the flow and heat transfer past a continuously moving porous plate in a stationary fluid has been analysed. The governing boundary layer equations have been reduced to a set of nonlinear ordinary differential equations using similarity transformations. The resulting boundary value problem has been solved numerically. The effects of magnetic and suction (or injection) parameters on the velocity and temperature profiles as well as on the skin friction and heat transfer coefficients have been studied. It has been observed that the effect of magnetic field is to increase the wall skin friction while the reverse occurs in the case of Nusselt number.

An exact solution for unsteady magnetohydrodynamic free convection flow with constant heat flux

Abstract The unsteady hydromagnetic free convection flow of a viscous incompressible and electrically conducting fluid generated by an impulsively moving vertical plate subject to constant heat flux at the plate has been considered. The dimensionless parameters governing the problem are the Prandtl number, the Grashof number and the Hartmann number. An exact solution has been obtained for this problem using Laplace transform. Velocity and skin friction of the flow have been presented for water, and the influence of the governing parameters has been discussed. In particular, the magnetic field has a retarding effect on the velocity while skin friction at the plate increases with it.

Unsteady Hydromagnetic Free Convection Flow with Heat Flux and Accelerated Boundary Motion

The effects of viscosity, magnetic field and buoyancy force on the unsteady free convection flow of an incompressible and electrically conducting fluid have been analysed when the flow is generated by uniformly accelerated motion of a vertical plate subject to constant heat flux. The resulting boundary value problem has been solved exactly for the temperature and velocity variables. The fluid velocity and the skin friction have been computed for some saturated liquids and the effects of the fluid and external forces have been discussed. It is observed that the increase in velocity caused by the larger heat flux can be controlled by enhancing the magnetic field strength. The skin friction at the boundary increases for larger Prandtl and Hartmann numbers, and decreases with increasing Grashof number.

Effect of rotation on unsteady hydromagnetic Couette flow

The effects of rotation and magnetic field on the Couette flow of an electrically-conducting fluid between two parallel plates have been discussed when one of the plates has been set into impulsive motion. Under the assumption of negligible induced magnetic field and the applied field being fixed relative to the moving plate, the governing momentum equations have been solved exactly, and the expressions for velocity and skin friction have been presented. The variations of velocity and skin friction have been discussed for different parameter values. The decrease in velocity due to rotation and its increase due to magnetic field have been shown.

Transient effects on magnetohydrodynamic couette flow with rotation: Accelerated motion

Abstract The transient features of the Couette flow of an electrically conducting fluid subject to rotation and magnetic field have been analysed when one of the plates has been set into uniformly accelerated motion. The resulting boundary value problem has been solved exactly and explicit expressions for the velocity and skin friction have been obtained. The variations of these with respect to the Hartmann and Ekman numbers have been shown. It is seen that the primary velocity increases with magnetic field and decreases with rotation, while the magnitude of secondary velocity has the opposite effect with respect to these processes.

Non-linear Convective Transport in a Binary Nanofluid Saturated Porous Layer

In this article, we study double-diffusive convection in a horizontal porous medium saturated by a nanofluid, for the case when the base fluid of the nanofluid is itself a binary fluid such as salty water. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis, while the Darcy model is used for the porous medium. The thermal energy equations include the diffusion and cross-diffusion terms. The linear stability is studied using normal mode technique and for non-linear analysis, a minimal representation of the truncated Fourier series analysis involving only two terms has been used. For linear theory analysis, critical Rayleigh number has been obtained, while non-linear analysis has been done in terms of the Nusselt numbers.

Finite difference analysis of unsteady hydromagnetic free-convection flow with constant heat flux

A numerical solution for unsteady hydromagnetic free-convection currents of a viscous incompressible and electrically conducting fluid induced by a vertical moving infinite plate is considered for constant heat flux at the plate. Velocity and skin-friction have been worked out for various values of the parameters occuring into the problem. It is found that magnetic parameter has a retarding effect on the velocity of air and water, while skin-friction increases with it.

On Laminar Boundary Layer Flow of Electrically Conducting Liquids Near an Accelerated Vertical Plate

The unsteady hydromagnetic flow of electrically conducting liquids whose Prandtl numbers are different from unity has been considered when the flow takes place near an infinite vertical flat plate subject to uniform heat flux and accelerated motion. A unified exact solution has been derived for the boundary layer velocity and skin friction for the cases of magnetic field being fixed relative to the fluid or to the vertical plate. The solution has been presented in real forms for fluids whose Prandtl numbers are greater than or less than unity. The response of the boundary layer fluid velocity to the variations in magnetic and buoyancy forces has been discussed for two sample fluids corresponding to the different Prandtl number categories. The influence of these forces on the skin friction has also been shown.

Free convection through a vertical channel in a rotating porous medium

Abstract The paper investigates the combined effect of viscous and Darcy dissipations in the case of a fully developed natural convection flow of an incompressible viscous fluid between two heated vertical walls in a rotating porous system. A perturbation method has been employed to obtain the solution of governing non-linear coupled equations. The zeroth order solution corresponds to the flow in the absence of viscous and Darcy dissipations. The effect of Darcy and Ekman numbers on the field variables and the mass flow rate has been discussed.

A numerical investigation of a buoyancy driven flow in a semi-porous cavity: comparative effects of ramped and isothermal wall conditions

Abstract Steady two-dimensional natural convection taking place in a rectangular cavity, partially filled with an isotropic porous material, has been investigated numerically using an ADI method. It is assumed that one of the vertical walls of the cavity has a ramped temperature distribution. The vorticity-stream function formulation has been used to solve the set of nonlinear partial differential equations governing the flows in the clear region and the adjoining porous region. The effects of Darcy number and Rayleigh number have been discussed in detail.