Abstract Bioconvection in porous media significantly influences numerous practical systems, such as bioengineering processes, microfluidic transport, wastewater management, and the optimization of microbial fuel cells and bioreactors. This study investigates the initiation of thermo-bioconvection in a porous layer containing the negative gravitactic microorganisms when subjected to local thermal non-equilibrium, confined between two horizontal surfaces subjected to bottom heating. The microorganisms mobility is modeled using Pedley's formulation, while fluid motion is governed by the Darcy–Brinkman framework. The governing equations are analyzed using a normal mode formulation, leading to an eigenvalue problem that is solved via the Galerkin method for free–free and rigid–rigid boundary conditions. The analysis reveals that the system exhibits only stationary convection, as the computed values of frequency remain negative under both types of boundary conditions. By enhancing the interphase heat transfer coefficient, system becomes stable as it raises the critical thresholds required for the initiation of both thermal and bioconvective instabilities. However, beyond a critical value (103), the effect gradually saturates especially for free–free boundaries. In contrast, higher swimming speed and lower cell diffusivity lead to earlier onset of instability. Furthermore, higher permeability pre-pones the onset of instability up to approximately 0.3, beyond which it remains nearly constant for both boundaries.
Yashika et al. (Fri,) studied this question.
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