Bioconvection of negatively geotactic microorganisms in a porous medium: the effect of cell deposition and declogging

A.V. Kuznetsov; N. Jiang

doi:10.1108/09615530310464535

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International Journal of Numerical Methods for Heat & Fluid Flow

ISSN: 0961-5539

Online from: 1991

Subject Area: Mechanical & Materials Engineering

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Bioconvection of negatively geotactic microorganisms in a porous medium: the effect of cell deposition and declogging

Document Information:
Title:	Bioconvection of negatively geotactic microorganisms in a porous medium: the effect of cell deposition and declogging
Author(s):	A.V. Kuznetsov, (Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC, USA), N. Jiang, (Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC, USA)
Citation:	A.V. Kuznetsov, N. Jiang, (2003) "Bioconvection of negatively geotactic microorganisms in a porous medium: the effect of cell deposition and declogging", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 13 Iss: 3, pp.341 - 364
Keywords:	Convection, Instability, Porous media
Article type:	Research paper
DOI:	10.1108/09615530310464535 (Permanent URL)
Publisher:	MCB UP Ltd
Abstract:	Mechanisms of deposition and declogging are considered while formulating a new continuum model for bioconvection in a dilute suspension of motile, negatively geotactic microorganisms in a porous medium. According to research in 1988, bioconvection is the name given to pattern-forming convective motions set up in suspensions of swimming microorganisms. “Negative geotaxis” means that the microorganisms tend to swim against the gravitational force. This paper is motivated by experimental research by Kessler who investigated the effect of porous media on the development of convection instability in algal suspensions. In the model suggested in this paper, the decrease of permeability due to cell adsorption by the porous medium is considered and the influence of this permeability decrease on the development of bioconvection is studied. The existence and stability of a two-dimensional plume in a rectangular enclosure with stress-free sidewalls is investigated. Governing equations include the Darcy law as well as the microorganism conservation equations. A conservative finite-difference scheme is utilized to solve these equations numerically. The analysis of the proposed model reveals that the major factors affecting the development of bioconvection are the initial permeability of the porous medium and the rate of cell deposition. For small permeability, the resistance to the fluid flow is too large, and bioconvection does not develop. If the rate of cell deposition is too large, the number of suspended cells quickly becomes too small because of cell capturing by the porous medium. For this reason, the critical density difference in the top fluid layer cannot be reached, and bioconvection does not develop.