Thermo-bioconvective transport in an oxytactic microorganisms-laden cavity

This study investigates heat and mass transfer in a square porous cavity containing oxytactic microorganisms using the Cattaneo–Christov heat flux model and Darcy flow. The governing equations, which incorporate the laws of mass, momentum, and energy conservation, are solved numerically using the finite-element method. Strong agreement is found when the Nusselt and Sherwood values are calculated and compared with the data provided in the black literature to validate the results. The results are calculated and thoroughly presented for a range of values of the physical parameters. Using streamlines, isotherms, concentration profiles and tables, the results show how different parameters like the Lewis number, the Peclet number, the Rayleigh number, and the bioconvection Rayleigh number affect heat and mass transfer with oxytactic microorganisms in the cavity. The cavity’s side walls further highlight how these characteristics affect the Nusselt and Sherwood numbers. With an emphasis on the influence of important physical parameters, the study often offers valuable information about the intricate relationships between heat, fluid flow, and microbe concentration within a porous cavity. It is observed that when the Péclet number increases from the baseline case of 0.1 to 13, the maximum value of the stream function increases by approximately 44. 2%, clearly highlighting the sensitivity of the flow field to variations in the advection strength. Similarly, as the Péclet number increases from 1 to 29, the minimum oxygen concentration decreases by almost 16.1%, indicating substantial oxygen depletion at higher Péclet values. An increase in the relaxation parameter from 0 to 2.55 results in a reduction of 41. 3% in the maximum value of the stream function, demonstrating the significant suppressive effect of relaxation on the convective strength of the flow. The presence of microorganisms improves heat transfer, with the Nusselt number increasing by approximately 15%–20% at low Prandtl numbers and exceeding 30% at higher Prandtl numbers, indicating a synergistic interaction between thermal stratification and bioconvection. Furthermore, as the oxygen consumption parameter increases, the minimum oxygen concentration is reduced by almost 12. 9%, indicating the dominant role of consumption over diffusion in shaping oxygen distribution within the cavity. These results are crucial to improve heat transmission and bioconvection processes in porous media, especially biological or ecological systems where microorganisms are important to dynamics.