UNSTEADY-FLOW OF A VISCOUS-FLUID BETWEEN 2 PARALLEL DISKS WITH A TIME-VARYING GAP WIDTH AND A MAGNETIC-FIELD

The unsteady incompressible viscous fluid flow between two parallel in finite disks which are located at a distance h(t) at time t* has been studied. The upper disk moves towards the lower disk with velocity h' (t). The lower disk is porous and rotates with angular velocity Omega (t). A magnetic field B(t*) is applied perpendicular to the two disks . It has been found that the governing Navier-Stokes equations reduce to a set of ordinary differential equations if h(t), a(t*) and B(t*) vary with time t in a particular manner, i.e. h(t*) = H(1 - alpha t*) (1/2), Omega(t) = Omega(0)(1 - alpha t*)(-1), B(t*) = B-0(1 - alpha t )(-1/2). These ordinary differential equations have been solved numer ically using a shooting method. For small Reynolds numbers, analytical solutions have been obtained using a regular perturbation technique. The effects of squeeze Reynolds numbers, Hartmann number and rotation of the disk on the flow pattern, normal force or load and torque have been studied in detail.