NIST Time|NIST Home|About NIST|Contact NIST

HomeAll Years:AuthorKeywordTitle2005-2010:AuthorKeywordTitle

Transport by Gravity Currents in Building Fires.


pdf icon Transport by Gravity Currents in Building Fires. (855 K)
Rehm, R. G.; McGrattan, K. B.; Baum, H. R.; Cassel, K. W.

International Association for Fire Safety Science. Fire Safety Science. Proceedings. Fifth (5th) International Symposium. March 3-7, 1997, Melbourne, Australia, Intl. Assoc. for Fire Safety Science, Boston, MA, Hasemi, Y., Editor(s), 391-402 pp, 1997.

Keywords:

fire research; fire safety; fire science; ceilings; building fires; heat transfer; gravity current; computational fluid dynamics; large eddy simulation

Abstract:

Gravity Currents (GC) are important physical phenomena which transport smoke and hot gases in corridors of buildings. In this paper, they are studied using large eddy simulations (LES). The transient Navier-Stokes (N-S) equations are numerically integrated with very high resolution, in two dimensions and with high resolution in three dimensions. The LES computations require no adjustable parameters, and are found to agree well with available experimental results in the absence of heat transfer. Fresh-water/salt-water experimental results are compared with computational results with adiabatic boundary conditions to demonstrate the validity of the model. Whereas, a high-resulution two-dimensional computation simulates very well the gravity current with adiabatic wall boundary conditions, significant wall heat transfer requires the consideration of three-dimensional effects. Heat transfer to the ceiling of a corridor from an underlying GC produces longitudinal convection rolls which significantly enhance heat losses to the ceiling and reduce the speed of progression of the GC down the corridor.