Computational study of backdraft dynamics and the effects of initial conditions in a compartment.

Backdraft dynamics and effects of initial fuel mass fraction on backdraft behavior were studied computationally using fire dynamics simulator with a Model-free simulation (MFS). The effects of one- and three-step reaction mechanisms on backdraft development and temporal pressure variation were examined. Thermal radiation effects were studied by considering the gray-gas-radiation (GRAY) and adiabatic model (ADIA). The gravity current and backdraft development were reasonably reproduced by the MFS. The temporal pressure rise inside the compartment showed a similar trend to previous experiments. ADIA did not predict the local ignition near the bottom wall, while GRAY did predict. The critical fuel mass fraction (Yf) for backdraft occurrence was determined from the two-peak characteristic in the pressure, and the predicted Yf was reasonable, compared with the experiments. Complex mixed combustion modes were found locally during backdraft development. MFS with finite chemistry was found to be a potentially good computational tool for backdraft dynamics. [ABSTRACT FROM AUTHOR]