Wolfram Jahn

The Effect of Model Parameters on the Simulation of Fire Dynamics

Peer-reviewed article published in the Proceedings of the 9th International Symposium on Fire Safety Science, Karlsruhe, 2008.

Flammability and the Heat of Combustion of Natural Fuels: A Review

Heat of combustion (HoC) is a key characteristic of fuels when analyzing and modeling wildfire scenarios. Despite significant differences in the structure of fuels from different environments, HoC is frequently considered a constant. This article briefly reviews methods used to describe natural fuels and the various different definitions of HoC. We also summarize measured values of HoC and elemental analyses of 238 plant genera reported in 28 papers since 1973. A statistical analysis of these data provided mean values and standard deviations of HoC for fuels according to six broad plant functional groups. Permutational Multivariate Analysis of Variance (PERMANOVA) demonstrated significant differences in the HoC with ground fuels and softwoods having particularly high values. Net heat of combustion was calculated for four fuel groups and the tabulated data may help to improve wildfire modeling and highlights fuels where further measurements of HoC are required.

Forecasting Fire Growth using an Inverse CFD Modelling Approach in a Real-Scale Fire Test

The rate of fire growth in a real-scale fire test is estimated using an inverse modelling approach of computational fluid dynamics (FDS v5). Measurements from the fire test are assimilated into the fire model and based on this the parameters of a decoupled fire growth model are estimated. A forecast of the fire development is then made with the estimated parameters. It is shown that a simplified fire growth model can give a robust representation of the underlying physics and that the necessary parameters can be estimated at an acceptable computational cost. The forecasts are shown to accurately predict the fire development. The results are based on a simplified single parameter fire growth model of a well characterized scenario, but the methodology allows for an extension to a more complicated model that would require less previous characterization of the fire scenario.