A DYNAMIC THERMAL INSULATOR - INDUCING RESONANCE WITHIN A FLUID-SATURATED POROUS-MEDIUM ENCLOSURE HEATED PERIODICALLY FROM THE SIDE

This theoretical and numerical study investigates the natural convecti on flow within a fluid saturated porous medium enclosure subjected to intermittent heating from the side (hot wall). A theory for predicting the natural convection frequency of the flow wheel circulating inside the enclosure is developed from the general porous medium equations o n a scaling basis. Physical insight indicates that heat flow resonance might occur when the input heat frequency matches the flow wheel circ ulating frequency. Numerical simulations confirm the existence of a pr eferred (resonance) input heat pulsating frequency. They also reveal t hat at the resonance frequency the fluid saturated porous medium syste m behaves as a dynamic thermal insulator in which the strong natural c onvection activity within the system, characterized by high amplitude heat flow oscillations, coexists with a damped oscillatory heat flux a t the isothermal (cold) wall.