Thermal-Bioconvection in a Rotating Phototactic Medium

Abstract Thermal-bioconvection in rotating phototactic suspensions plays a pivotal role in optimizing processes within biofuel systems, photobioreactors, and microbial ecosystems by enhancing fluid transport and biomass distribution. This study explores the complex interaction between thermal gradients and phototactic responses in a rotating suspension of micro-organisms confined between a rigid lower boundary and a stress-free upper surface. The system undergoes uniform vertical-axis rotation, and stability characteristics are examined using matlab's bvp4c solver. The analysis examines how key dimensionless parameters, the Taylor number, the thermal Rayleigh number, the Lewis number, and the critical total light intensity, govern bioconvection onset. Results indicate that the critical bioconvection Rayleigh number rises with increasing rotational strength (Taylor number) but decreases with higher thermal driving (Rayleigh number), enhanced Lewis number, and greater phototactic sensitivity. Interestingly, the critical thermal Rayleigh number remains largely unaffected by the Lewis number and light intensity but is sensitive to variations in rotation. These insights underscore the importance of thermal and rotational coupling in shaping phototactic bioconvection, with direct implications for the design and control of efficient biotechnological fluid systems.