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Journal of Porous Media
IF: 1.49 5-Year IF: 1.159 SJR: 0.504 SNIP: 0.671 CiteScore™: 1.58

ISSN Print: 1091-028X
ISSN Online: 1934-0508

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Journal of Porous Media

DOI: 10.1615/JPorMedia.v11.i8.40
pages 751-764

Gravitactic Bioconvection in a Fluid-Saturated Porous Medium with Double Diffusion

Tri Nguyen-Quang
Dalhousie University, Truro, NS, Canada
The Hung Nguyen
Department of Mechanical Engineering, Ecole Polytechnique, Montréal, Canada
Georges Le Palec

ABSTRACT

This paper examines the combined effects of density stratifications in porous media due to both gravitactic microorganism motion and thermal or solutal solicitation. These effects are coined in the literature by the term "double diffusion." In this case, an equation of conservation of energy or mass is added to the gravitactic bioconvection system. The problem is then governed by two Rayleigh numbers, a Peclet number (normalized swimming speed), and a Lewis number (ratio of thermal diffusivity/microorganism diffusivity). It is found that gravitactic bioconvection with double diffusion may contain a subcritical instability regime due in part to the gravitactic motion of microorganisms and in part to the weak diffusivity of the thermal/solutal solicitation. It is also found that there is an oscillatory regime that is established below the critical threshold of steady bioconvection. This oscillatory convection flow may arise when the diffusivity of the stabilizing component is weaker than that of the destabilizing component.


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