The sensitivity of modeled flight distance to the lofting to transport transition criterion in coupled ember flight models

摘要

The results of a series of numerical simulations of ember flight are presented. The simulations model both the lofting of the ember by the rising column of air above the fire, and the horizontal transport of the embers due to the atmospheric boundary layer flow. Simulations were run to examine the sensitivity of the predicted flight distance to the choice of lofting to transport transition model. Three transition models were examined, a fully de-coupled model where the ember is only transported horizontally once it has been lofted to its maximum height, a coupled model where the ember is transported and lofted simultaneously, and a capped height model. The flight distance is very sensitive to the choice of transition model. The influence of turbulent fluctuations on the flight distance was also examined. It was found that turbulence occasionally lead to shorter predicted flight distances than those predicted by the mean flow model. Given the sensitivity of the predicted flight distance to the transition model it is essential to conduct a series of wind tunnel verification experiments.