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Instability of double-diffusive convection in Voigt fluid-saturated porous media under local thermal non-equilibrium
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DOI：10.1016/j.jppr.2026.02.005.png)
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Abstract
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This study examines the linear instability of double-diffusive convection in a horizontal porous layer saturated with a Kelvin-Voigt viscoelastic fluid under local thermal non-equilibrium (LTNE) conditions, where the fluid and solid phases maintain distinct temperatures. Such systems are essential for advancing thermal management in engineering applications and for understanding natural geophysical processes involving coupled heat and mass transport. Using linear stability analysis with normal-mode solutions, we determine the critical conditions for the onset of stationary and oscillatory convection, emphasizing the roles of solute transport, viscoelasticity, porous-medium characteristics, and interphase heat transfer. Our findings demonstrate that oscillatory convection prevails across a broad parameter space, with viscoelastic effects either stabilizing or destabilizing depending on the intensity of solutal stratification. Specifically, increasing the solute Darcy-Rayleigh number substantially elevates the critical thermal Rayleigh number, while higher Darcy numbers promote viscous diffusion and broaden the stability domain. In contrast, elevated Darcy-Prandtl and Lewis numbers accelerate the onset of oscillatory convection by amplifying thermal and concentration gradients. The interphase heat transfer coefficient exerts a pronounced stabilizing influence, especially within the intermediate LTNE regime, whereas the weighted conductivity and thermal diffusivity ratios yield contrasting effects on system stability. We validate our critical thresholds against established Newtonian fluid benchmarks, confirming the accuracy and robustness of our analysis. The key novelty of this work lies in the systematic quantification of the coupled effects of viscoelasticity, solute transport, and interphase heat transfer on the onset of oscillatory convection under thermal non-equilibrium conditions. These results offer valuable insights for designing chemical reactors, geothermal energy systems, and heat exchangers, as well as for environmental modeling of oceanic and atmospheric flows in porous media containing viscoelastic fluids.
Keywords:
Convection
Heat and mass transfer
Kelvin-Voigt fluid
Local thermal non-equilibrium
Instability
Porous medium
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