Thermal instability of a Walters' (model B′) elastico-viscous fluid in the presence of variable gravity field and rotation in porous medium

The problem of thermal instability of a Waiters' (model B ') viscoelastic fluid in a porous medium is considered ill the presence of a variable gravity field and rotation. It is found that the principle of exchange of stabilities is valid under certain conditions. For stationary convection, the Waiters' (model B ') elastico-viscous fluid behaves like a Newtonian fluid. It is found that rotation has stabilizing effect as gravity increases upward and a destabilizing effect as gravity decreases upward, the medium permeability has stabilizing/destabilizing effects depending on the rotation parameter, gravity is considered to be increasing upward from its value g (i.e. lambda > 0). The effects of rotation and the medium permeability on thermal instability have also been shown graphically. The sufficient conditions for the non-existence of overstability are also obtained.