Forest fires cost the United States millions of dollars per year in property and land loss and were responsible for the deaths of numerous firefighters and civilians last year. In addition, this year, there have been highly publicized aviation disasters that have occurred in attempting to extinguish the infernos.

What if the likely ignition locations of these fires could be predicted? What if the spread of these fires could be predicted and therefore controlled before becoming uncontrollable? Unusually for a CFD challenge this is not about reducing design costs, nor about meeting production deadlines: it is, however, about protecting the environment and saving property and lives where the deadlines are even more critical.

Leading the research and development of forest fire management are the team of engineers and scientists at the US Forest Service’s Fire Sciences Laboratory in Missoula, Montana. They have recently acquired STAR-CD to further advance their already comprehensive numerical modeling techniques and gain a better understanding of how to contain and minimize forest fire spread. Their facility is equipped with an instrumented wind tunnel burn-rig, capable of burning a range of solid fuels in a controlled environment and generating valuable data. The study of fire growth in the wind tunnel can then be compared to predictions performed using STAR-CD in an effort to correlate combustion and turbulence models required to predict this chaotic flow domain.

On the macro-environment scale, analyses carried out by the Forest Service using STAR-CD have involved the study of the flow of large air masses over topo-graphical domains. Using satellite-based digital elevation map (DEM) data, the landscape surface can be read automatically into STAR-CD to provide an immediate shell representation of the ground surface. The CD adapco Group worked together with the Fire Sciences lab to develop this automated process to build the computational model based on the DEM data. Once the boundary conditions have been added, which represent actual measured wind velocities in both 3-D spatial and temporal reference frames, the analysis can be run and results post-processed all within STAR-CD.

The ability of STAR-CD’s modular framework to interact with third party codes and in-house software has been a major boost to the Scientists and Engineers at the Fire Research Center. Using STAR-CD as the backbone of their computational effort, the investment in their existing in-house codes is protected by linking these directly to STAR-CD to produce a dedicated framework suited to highly specific problems. This approach is exemplified by the creation of dedicated user-panels to fully automate the analysis set-up, execution and post-processing.

Future work will include the analysis of local buoyancy effects due to fire progression and also the impact of solar radiation on mountain slopes, which can act as a catalyst in the spread of vegetation fire.

PROSTAR surface representation of 7 mile square digital elevation map.

Pressure contours for 9 m/s wind speed.

Velocity magnitude contours for 9 m/s wind speed.