Large eddy simulation of backdraft phenomena on a 2/5th scale compartment

Among building fires, backdraft is a phenomenon that poses great danger to occupants and first responders. It may occur when a heated and oxygen depleted closed compartment holds significant unburned fuel concentrations. When an opening to the exterior is established, a cold air current can introduce oxygen back in the enclosure. If ignition conditions are adequate, the flammable mixture can ignite producing a fireball that travels across the opening. It is of great interest to understand and simulate the detailed fire physics behind backdraft. The Fire Dynamics Simulator (FDS) is an engineering tool for simulation of fire scenarios in forensic studies and fire protection systems design. FDS solves the Low Mach approximation equations for thermally driven buoyant flows by means of Large Eddy Simulation (LES), including combustion and radiation physics.

In this talk, we will describe the work being done at NIST on FDS simulation of backdraft phenomena. We target model validation against the detailed thermal and mixture composition measurements done at the National Fire Research Laboratory on a compartment with 2/5th the dimensions of the standard ASTM fire test room (NIST Technical Note 2185). A fire model assessment on different experimental cases will be provided.