Convective instability in periodically heated superposed fluid-porous layer systems with asymmetric boundary conditions
Phys. Rev. Fluids 10, 113502 – Published 26 November, 2025
DOI: https://doi.org/10.1103/r1dz-nw68
Abstract
The present study illustrates the effect of periodic heating on the onset of convective instability in a two-layer system composed of a fluid layer overlying a Darcy porous medium. The system is bounded below by a sinusoidally heated impermeable surface and above by a stress-free surface. A general thermal boundary condition depicts the heat transfer through the upper surface. Tangential and normal stress balances at the permeable fluid-porous interface are represented by the Beavers-Joseph-Saffman-Jones and Lions interface conditions, respectively. Linear and energy stability analyses are performed, and the resulting stability criteria are determined through numerical computations. The linear theory results indicate that varying modulation parameters can not only control the onset of instability but also induce a shift in the mode (fluid/porous) of instability when . The investigation is further extended to systems with varying configurations by altering the physical parameters such as Biot number, thermal diffusivity ratio, slip coefficient, and Darcy number. The energy method yields two nonlinear stability criteria—strong global and asymptotic limits—and hence dismisses the existence of global stability. These nonlinear bounds lead to the regions of subcritical instability and uncertain stability.
