Rayleigh-Bénard-Marangoni Instability in a Self-rewetting Fluid Layer Overlying a Porous Medium

Rayleigh-Bénard-Marangoni instability in a bilayer system of self-rewetting fluid overlying a porous medium is investigated. The upper surface of the fluid layer is assumed non-deformable and a constant temperature gradient is imposed. Unlike in previous works, self-rewetting fluid is considered in this paper, whose surface tension is a quadratic function of temperature. As a result, it would reinforce or suppress the instability caused by buoyancy in different scenarios. Thorough study is carried out and the influence of depth ratio h, Rayleigh number Ra and Biot number Bi on instability of the system is discussed. It was found that the marginal curve is bimodal in certain combination of parameters and mode transition of convection is also found.