Norzieha Mustapha

Unsteady magnetohydrodynamic blood flow through irregular multi-stenosed arteries

Flow of an electrically conducting fluid characterizing blood through the arteries having irregular shaped multi-stenoses in the environment of a uniform transverse magnetic-field is analysed. The flow is considered to be axisymmetric with an outline of the irregular stenoses obtained from a three-dimensional casting of a mild stenosed artery, so that the physical problem becomes more realistic from the physiological point of view. The marker and cell (MAC) and successive-over-relaxation (SOR) methods are respectively used to solve the governing unsteady magnetohydrodynamic (MHD) equations and pressure-Poisson equation quantitatively and to observe the flow separation. The results obtained show that the flow separates mostly towards the downstream of the multi-stenoses. However, the flow separation region keeps on shrinking with the increasing intensity of the magnetic-field which completely disappears with sufficiently large value of the Hartmann number. The present observations certainly have some clinical implications relating to magnetotherapy which help reducing the complex flow separation zones causing flow disorder leading to the formation and progression of the arterial diseases.

UNSTEADY RESPONSE OF BLOOD FLOW THROUGH A COUPLE OF IRREGULAR ARTERIAL CONSTRICTIONS TO BODY ACCELERATION

A two-dimensional (2D) nonlinear mathematical model to study the response of the pulsatile flow of blood through a couple of irregular stenoses influenced by externally imposed periodic body acceleration is developed. The model is 2D and axisymmetric with an outline of the stenosis obtained from the three-dimensional (3D) casting of a mildly stenosed artery. The combined influence of an asymmetric shape and surface irregularities of the constrictions is explored in a computational study of blood flow through arterial stenoses with 48% areal occlusion. The arterial wall is treated as an elastic (moving wall) cylindrical tube having a couple of stenoses in its lumen, while the streaming blood is considered to be Newtonian. Solutions of the time-dependent nonlinear Navier–Stokes equations in the cylindrical coordinate system are obtained using a finite difference method based on the nonuniform and nonstaggered grids. The finite difference approximation helps to estimate the effects of body acceleration on the doubly constricted flow phenomena through several graphical representations quantitatively in order to validate the applicability of the present, improved mathematical model.

Unsteady magnetohydrodynamic oscillatory flow of viscoelastic fluids in a porous channel with heat and mass transfer

In this paper, we analyze the effects of slip condition on the unsteady magnetohydrodynamic (MHD) flow of incompressible viscoelastic fluids in a porous channel under the influence of transverse magnetic field and Hall current with heat and mass transfer. The channel flow is induced due to external pressure gradient of oscillatory form. The governing equations for the velocity field, temperature and concentration distributions, are solved using perturbation technique. We present the results for skin friction, Nusselt number and Sherwood number. The numerical results are also computed for skin friction in tabular form. The effects of various indispensable flow parameters are displayed using several graphs. The numerical results show the effects of the physical parameters on the fluid flow as well as on heat and mass transfer and skin friction. The solutions for Newtonian fluids can be obtained as a limiting case from our general solutions when the viscoelastic parameter is zero.

Effects of Hall Current and Mass Transfer on the Unsteady Magnetohydrodynamic Flow in a Porous Channel

The combined effects of Hall current and mass transfer on the unsteady magnetohydrodynamic (MHD) flow of a viscous fluid passing through a porous channel have been investigated. The flow in the fluid has been induced due to external pressure gradient. The closed form analytical solutions have been obtained for the velocity, temperature and concentration fields. The analytical expressions for non-dimensional Skin-friction, Nusselt number and Sherwood number have been computed. The influence of various embedded flow parameters have been analyzed through graphs. The solutions obtained show that the influence of Hall parameter and mass transfer phenomenon give some interesting results. It is found that the Hall parameter have an increasing effect on the fluid velocity and approaches to the steady state as the time parameter is increased. The fluid concentration is increased for larger values of Peclet and Schmidt numbers whereas decreased with increase in Soret number and time parameter.

Unsteady Two-Dimensional Blood Flow in Porous Artery with Multi-Irregular Stenoses

The flow characteristics of an unsteady axisymmetric two-dimensional (2D) blood flow in a diseased porous arterial segment with flexible walls are investigated. The arterial walls mimic the irregular constrictions whereas the lumen containing the thrombus, cholesterol, and fatty plaques represents the porous medium. The governing equations with appropriate initial and boundary conditions are solved numerically using MAC method. The discretization is done on staggered grid with non-uniform grid size and pressure-poisson equation is solved following SOR method. The pressure and velocity corrections are made cyclically until the steady state is achieved. It is observed that for decreasing permeability, flow is highly decelerated while pressure drop and wall shear stress increases. The separation zones and re-circulation regions are found for severe stenoses. Flow separation and re-circulation diminishes for decreasing permeability of the porous medium. Comparisons are provided with published experimental and numerical results.

Simultaneous effects of dissipative heating and partial slip on peristaltic transport of Sisko fluid in asymmetric channel

This paper looks at the dissipative heat transfer on the peristaltic flow of a Sisko fluid in an asymmetric channel. Flow exhibits slip at the channel walls maintained at nonuniform temperatures. Long wavelength approximation is utilized and perturbation solutions are obtained about Sisko fluid parameter. Closed form solutions for the stream function, axial pressure gradient, axial velocity, temperature and the heat transfer coefficient are presented. Influences of various interesting parameters are presented in graphical and tabular forms. Pumping and trapping phenomena are discussed for increasing velocity slip parameter. A comparative study on temperature and heat transfer coefficient for viscous, shear thinning and shear thickening fluids has been presented. Comparisons for viscous fluid are found in good agreement.

Non-linear peristaltic flow of Walter's B fluid in an asymmetric channel with heat transfer and chemical reactions

In this paper, effects of heat and mass transfer on peristaltic transport of Walters B fluid in an asymmetric channel are investigated. The governing equations are solved using regular perturbation method by taking wave number as a small parameter. Expressions for the stream function, temperature distribution, heat transfer coefficient, and mass concentration are presented in explicit form. Solutions are analyzed graphically for different values of arising parameters such as viscoelastic parameter, Prandtl, Eckert, Soret, Schmidt, and Reynolds number. It has been found that these parameters considerably affect the considered flow characteristics. Results show that with an increase in Eckert and Prandtl number temperature and heat transfer coefficient increase while mass concentration decreases. Further, Mass concentration also decreases with increasing Soret and Schmidt number.

Transient oscillatory flows of a generalized Burgers' fluid in a rotating frame

In this paper, the unsteady oscillatory flows of a generalized Burgers’ fluid in a rotating frame are investigated. The constitutive equations of the generalized Burgers’ fluid are used in the mathematical formulation of the problem. The solutions are obtained by using the Laplace transform method. The graphical results are displayed and discussed for various parameters of interest. It is found that the velocity profiles reflect some interesting results for the rotation parameter and rheological fluid parameters.

Thermal diffusion and diffusion thermo effects on peristaltic flow of sisko fluid in nonuniform channel with dissipative heating

This investigation deals with thermal diffusion and diffusion thermo effects on the peristaltic flow of a Sisko fluid in an asymmetric channel. The mode of dissipative heat transfer is taken into account with nonuniform wall temperatures. Long wavelength approximation is utilized. Solutions for the highly nonlinear coupled governing equations involving power law index as an exponent are derived by employing the perturbation technique in a Sisko fluid parameter. Closed form solutions for the stream function, the axial pressure gradient, the skin friction, the temperature, the concentration, and the Nusselt number are presented. Effects of various interesting parameters are graphically interpreted. A comparative study between Newtonian, shear thinning, and shear thickening fluids is also presented. Comparison with published results for the case of viscous fluid is observed in good agreement.