Transport By Gravity Currents In Building Fires

Abstract

Gravity currents (GC) are important physical phenomena which transport smoke and hot gases id corridors of buildings. In this paper, they are studied using l q e 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-resolution 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.