Linear stability analysis of electroconvection in a polarized dielectric porous layer with couple stresses under a sinusoidally time-varying electric potential

The linear stability of electroconvection in a horizontally oriented, thermally unstable dielectric fluid layer saturated with a Darcy porous medium and influenced by couple-stress effects are investigated. The system is subjected to a sinusoidally time-varying electric potential applied at the boundaries. The novelty of this work lies in the combined effects of couple stresses, electric field modulation, and Darcy-porous medium, an area not extensively explored in the existing literature. Using the Boussinesq approximation and a regular perturbation technique, we deal with the governing eigenvalue problem and analyze the critical conditions for the onset of convection. The analysis reveals that electric field modulation can exert either a stabilizing or destabilizing influence depending on the modulation frequency and material parameters. At low frequencies, the destabilizing role of the electric Rayleigh number becomes more pronounced, while couple stress effects contribute to system’s stabilization. Additionally, the Vadasz number significantly modifies the stability behavior, enhancing the effects of modulation at high frequencies. Our findings highlight the potential of electric field modulation as a viable mechanism for controlling therma l instability in particle-laden dielectric fluids confined within porous structures. The results provide new insights into electrohydrodynamic flow control in engineering systems involving smart fluids and porous media.