A STUDY OF SOME TIME-DEPENDENT FLOWS IN MAGNETOHYDRODYNAMICS

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Date
2012-04
Authors
CLEMENT, ADEDAYO APERE
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Abstract
The motion of an electrically conducting fluid in two types of geometries is studied; namely a channel formed by two parallel plates and an annulus formed by two concentric cylinders. The fluid flow is assumed to be unsteady, laminar and incompressible with a magnetic field applied perpendicular to the flow direction. It is also assumed that no applied or polarization voltage exists. We have considered different physical situations and factored the effect of Hall and ion-slip currents in some cases. The system of partial differential equations describing the different flow problems has been formulated and unified closed form expressions are obtained for both cases of the applied magnetic field being fixed to either the fluid or the moving wall where applicable. The Laplace transform techniques are used to reduce the system of partial differential equations to ordinary differential equations; the resulting boundary value problems are then solved analytically. However, the Riemann-sum approximation method is used to invert the Laplace domain to the time domain where direct inversion is difficult. The corresponding steady state equations are derived where appropriate and solved analytically to double check the results. Also, the implicit finite difference method is used to verify the Riemann-sum approximation method. MATLAB programmes are written to compute and generate the graphs for the velocities and the skin frictions. A parametric study depicting the effect of the various dimensionless parameters on the velocity and skin friction is conducted. These parameters include the Ekman number E, the Hall parameter /3„ ion-slip parameter /3„ the suction/injection parameter S, the Hartmann number Ha and time r\ amongst others. The effects of changing the parameters mentioned above are observed either to increase, to decrease or to have no effect on the velocity profiles and the skin friction.
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A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES AHMADU BELLO UNIVERSITY ZARIA, NIGERIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF DOCTOR OF PHILOSOPHY IN MATHEMATICS DEPARTMENT OF MATHEMATICS FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY ZARIA, NIGERIA
Keywords
TIME-DEPENDENT ,, FLOWS,, MAGNETOHYDRODYNAMICS
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