Fire Safety Science Digital Archive

This paper summarizes a series of salt water experiments that resemble the smoke flow in the early stages of a residential scale building fire. Experimental measurements of the fluid density of the salt water flow field are made using the Laser Induced dye Fluorescence (LIF) technique. The salt water experiments are then simulated using the Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) computational techniques that are available within the Fire Dynamics Simulator (FDS) computer fire model. Computations, using each technique, are conducted at a number of different grid resolutions. The comparison of computational results and experimental measurements show that the LES technique performs better at coarse grid resolutions, due primarily to the computational stability requirement for an artificially high fluid viscosity in DNS, which inhibits turbulent mixing. The LES computations were capable of resolving the flow field features that are evident in the experimental density measurements when the uniform grid resolution has a characteristic dimension that is less than the vertical extent of the domain divided by fifty. Generally speaking, at high grid resolutions, the agreement between experimental measurements and the LES computational results were very good.