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RESEARCH ARTICLE
Contents Vol 14(1)

Coherent vortical structures in numerical simulations of buoyant plumes from wildland fires

Philip Cunningham A E , Scott L. Goodrick B , M. Yousuff Hussaini C and Rodman R. Linn D
+ Author Affiliations
- Author Affiliations

A Department of Meteorology and Geophysical Fluid Dynamics Institute, The Florida State University, Tallahassee, FL 32306, USA.

B USDA Forest Service, Southern Research Station, Athens, GA 30603, USA.

C School of Computational Science and Information Technology, The Florida State University, Tallahassee, FL 32306, USA.

D Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.

E Corresponding author. Telephone: +1 850 644 4334; fax: +1 850 644 9642; email: cunningham@met.fsu.edu

International Journal of Wildland Fire 14(1) 61-75 https://doi.org/10.1071/WF04044
Submitted: 31 August 2004  Accepted: 19 October 2004   Published: 7 March 2005

Abstract

The structure and dynamics of buoyant plumes arising from surface-based heat sources in a vertically sheared ambient atmospheric flow are examined via simulations of a three-dimensional, compressible numerical model. Simple circular heat sources and asymmetric elliptical ring heat sources that are representative of wildland fires of moderate intensity are considered. Several different coherent vortical structures that dominate the plume structure and evolution are evident in the simulations, and these structures correspond well with those observed in plumes from wildland fires. For the circular source, these structures include: (i) a counter-rotating vortex pair aligned with the plume trajectory that is associated with a bifurcation of the plume, (ii) transverse shear-layer vortices on the upstream face of the plume, and (iii) vertically oriented wake vortices that form periodically with alternating sign on either side of the downstream edge of the plume base. For the elliptical ring source, a streamwise counter-rotating vortex pair is apparent on each flank, and a transverse horizontal vortex is observed above the head of the source. In all simulations the plume cross section is represented poorly by a self-similar Gaussian distribution.


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