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Enhanced tracer transport by the spiral defect chaos state of a convecting fluid

Chiam, K.-H. and Cross, M. C. and Greenside, H. S. and Fischer, P. F. (2005) Enhanced tracer transport by the spiral defect chaos state of a convecting fluid. Physical Review E, 71 (3). Art. No. 036205. ISSN 1539-3755. doi:10.1103/PhysRevE.71.036205.

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To understand how spatiotemporal chaos may modify material transport, we use direct numerical simulations of the three-dimensional Boussinesq equations and of an advection-diffusion equation to study the transport of a passive tracer by the spiral defect chaos state of a convecting fluid. The simulations show that the transport is diffusive and is enhanced by the spatiotemporal chaos. The enhancement in tracer diffusivity follows two regimes. For large Péclet numbers (that is, small molecular diffusivities of the tracer), we find that the enhancement is proportional to the Péclet number. For small Péclet numbers, the enhancement is proportional to the square root of the Péclet number. We explain the presence of these two regimes in terms of how the local transport depends on the local wave numbers of the convection rolls. For large Péclet numbers, we further find that defects cause the tracer diffusivity to be enhanced locally in the direction orthogonal to the local wave vector but suppressed in the direction of the local wave vector.

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Additional Information:©2005 The American Physical Society (Received 23 September 2004; published 11 March 2005) This work was supported by the Engineering Research Program of the Office of Basic Energy Sciences at the Department of Energy, Grants No. DE-FG03-98ER14891 and No. DE-FG02-98ER14892. We acknowledge the Caltech Center for Advanced Computing Research and the North Carolina Supercomputing Center. We thank Tony Leonard and Dan Meiron for useful discussions, as well as Janet Scheel for her generous help with carrying out the computations.
Subject Keywords:chaos; convection; spatiotemporal phenomena; numerical analysis; diffusion; tracers
Issue or Number:3
Record Number:CaltechAUTHORS:CHIpre05
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5169
Deposited By: Archive Administrator
Deposited On:04 Oct 2006
Last Modified:08 Nov 2021 20:23

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