Effect of small particles on the stability of bioconvection in a suspension of gyrotactic microorganisms in a layer of finite depth

The purpose of this paper is to investigate the effect of small particles that are heavier than water on the stability of a suspension of motile gyrotactic microorganisms in a horizontal fluid layer of finite depth. If bioconvection develops, it enhances mixing and slows down the settling of the particles, which may be important in pharmaceutical applications. A linear stability analysis is utilized to investigate this problem. It is established that the critical Rayleigh number increases with the increase of the average number density of small particles, which means that the particles make the suspension more stable. (C) 2004 Elsevier Science Ltd.