Bioconvection of gravitactic microorganisms in a fluid layer

A study is made of the spontaneous pattern formation of gravitactic microorganisms in a horizontal fluid layer. The linear stability theory is used to determine the onset of convection in terms of the Rayleigh number and the swimming velocity. It is found that the onset of convection in a gravitactic suspension may be very different from that of Bénard cells under the well-known fixed-flux heating condition.