Simulating Fire Whirls.
Simulating Fire Whirls.
(1693 K)
Battaglia, F.; McGrattan, K. B.; Rehm, R. G.; Baum, H.
R.
NISTIR 6341; 22 p. July 1999.
Combustion Theory and Modelling, Vol. 4, 123-138, 2000.
Available from:
National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
Telephone:
1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900.
Website: http://www.ntis.gov
Order number: PB99-158339
Keywords:
flame whirls; fire plumes; circulation; combustion
models; buoyancy
Abstract:
A numerical investigation of swirling fire plumes is
pursued to understand how swirl alters the plume
dynamics and combustion. One example is the 'fire
whirl' which is known to arise naturally during forest
fires. This buoyancy-driven fire plume entrains ambient
fluid as heated gases rise. Vorticity associated with a
mechanism such as wind shear can be concentrated by the
fire, creating a vortex core along the axis of the
plume. The result is a whirling fire. The current
approach considers the relationship between buoyancy and
swirl using a configuration based on fixing the heat
release rate of the fire and imposing circulation.
Large eddy methodologies are used in the numerical
analyses. Results indicate that the structure of the
fire plume is significantly altered when angular
momentum is imparted to the ambient fluid. The vertical
acceleration induced by buoyancy generates strain fields
which stretch out the flames as they wrap around the
nominal plume centerline. The whirling fire constricts
radially and stretches the plume vertically.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899