CONVECTION AND STABILITY IN A ROTATING POROUS LAYER WITH ALTERNATING DIRECTION OF THE CENTRIFUGAL BODY FORCE

An alternating direction of the centrifugal body force results when th e axis of rotation is placed within the boundaries of a rotating fluid saturated porous layer. The onset of thermal convection and stability in a fluid saturated porous layer prevailing such conditions is inves tigated analytically. The marginal stability criterion was evaluated i n terms of a critical centrifugal Rayleigh number and a corresponding critical wave number. The effect of the offset distance of the layer's cold wall from the axis of relation on the convection is analyzed, sh owing that the critical centrifugal Rayleigh and wave numbers increase significantly as the layer's cold wall move away from the rotation ax is. This leads eventually to unconditional stability when the layer's hot wall coincides with the rotation axis. This unconditional stabilit y prevails when the axis of rotation moves away from the porous domain , so that the imposed temperature gradient opposes the direction of th e centrifugal acceleration. Significant effects on the convection patt ern are identified as a result of the rotation axis location.