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Large Eddy Simulations of Smoke Movement in Three Dimensions.


pdf icon Large Eddy Simulations of Smoke Movement in Three Dimensions. (920 K)
Baum, H. R.; McGrattan, K. B.; Rehm, R. G.

NISTIR 6030; June 1997.

Interscience Communications Ltd.; National Institute of Standards and Technology; Building Research Establishment; and Society of Fire Protection Engineers; Swedish National Testing and Research Institute. Interflam '96. International Interflam Conference, 7th Proceedings. March 26-28, 1996, Cambridge, England, Interscience Communications Ltd., London,England, Franks, C. A.; Grayson, S., Editors, 189-198 pp, 1996 AND U.S./Japan Government Cooperative Program on Natural Resources (UJNR). Fire Research and Safety. 13th Joint Panel Meeting. Volume 1. NISTIR 6030. March 13-20, 1996, Gaithersburg, MD, Beall, K. A., Editor, 249-258 pp, 1997 AND European Symposium on Fire Safety Science, First (1st). ABSTRACTS. Session II. CFD 1. Proceedings. ETH Institute for Structural Engineering, Zurich, Switzerland, II-5/75-76, August 21-23, 1995, 1997.

Available from:

National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161.
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ON BOOK SHELF: TH9112.I57 1996
Order number: PB97-184204

Keywords:

fire safety; smoke measurement; simulation; mathematical models; equations; smoke transport; high temperature gases; enclosures

Abstract:

This paper describes a methodology for simulating the transport of smoke and hot gases in enclosures. The approach is based on the use of efficient CFD techniques and high performance computers to solve a form of the Navier Stokes equations specialized to the smoke movement problem. The fire is prescribed in a manner consistent with a mixture fraction based approach to combustion, but the combustion phenomena themselves are not simulated. The mixing and transport of smoke and hot gases is calculated directly from an approximate form of the Navier Stokes equations. The computations are carried out as a three-dimensional time-dependent process, limited only by the spatial resolution of the underlying grid. No turbulence models are employed; the large scale eddies are simulated directly and sub-grid scale motions are suppressed. Present capabilities permit a typical residential room or hotel unit to be simulated at a 3-5 centimeter resolution limit, with correspondingly coarser resolution for larger spaces. The enclosure can have any shape made up of rectangular blocks, and can be multiply connected. The smoke is simulated by tracking a large number of Lagrangian elements, which originate in the fire. These same elements carry the heat released by the fire, providing a self consistent description of the smoke transport at all resolvable length and time scales. Large temperature and pressure variations are permitted, subject to the limitation that the Mach number is much less than one. The next two sections give a brief description of the mathematical and computational aspects of the model, while the final section illustrates its capability with sample results and a comparison with experiment.