title: Onset of thermovibrational filtration convection: departure from thermal equilibrium.
abstract: A theoretical investigation is made to understand the onset of thermovibrational convection in a fluid saturated horizontal porous layer subjected to isothermal heating either at the bottom or at the top. Attention is paid to the situation in which the solid and fluid phases of the porous medium may fail to obey thermal equilibrium locally. Vertical harmonic vibrations of arbitrary amplitude and frequency are considered. The threshold for dynamic instability is found via synchronous and subharmonic resonant modes exploiting the Floquet theory. The nonequilibrium effect is felt only for intermediate values of the interphase heat transfer coefficient H. It is found that H restrains the onset of convection whereas γ, the porosity modified conductivity ratio, encourages it. γ constricts the convective cells ensuing at the threshold except when the layer heated from below is undergoing small amplitude vibrations. Small values of γ expose the competition between synchronous and subharmonic modes for a wider range of vibrational frequencies.
authors.affiliation: Department of Mathematics, Bharathiar University, Coimbatore 641 046, Tamil Nadu, India. sshravan@lycos.com
authors.forename: S
authors.initials: S
authors.lastname: Saravanan
authors.forename: T
authors.initials: T
authors.lastname: Sivakumar