Numerical investigation of bioconvection of gravitactic microorganisms in an isotropic porous medium

A new continuum model is formulated for bioconvection in a dilute suspensio n of swimming, gravitactic microorganisms in a porous medium. "Bioconvectio n" is the name given to pattern-forming convective motions set up in suspen sions of swimming microorganisms. "Gravitaxis" means that microorganisms te nd to swim against the gravity. The aim of this paper is to analyze collect ive behavior and pattern formation in populations of swimming microorganism s. The existence and stability of a two-dimensional plume in a tall, narrow chamber with stress-free sidewalls is investigated. Governing equations in clude Darcy law as well as microorganism conservation equation. A conservat ive finite-difference scheme is used to solve these equations numerically. (C) 2001 Elsevier Science Ltd.