Experimental and Modeling Study of Risk from Ember Storms

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Spot fires in wildfire environment are caused by embers lofted into the atmosphere and blown well ahead of the main front of the wildfire. The objective of this research is to establish an experimentally verified stochastic model for ember flight in wildfires. The research program will build on existing deterministic models for ember flight and develop analytical and numerical models that account for the inherently stochastic nature of the problem. The models will include parameterizations of the probability distribution functions for ember size and shape, fire size and intensity, and the turbulent velocity fluctuations in fire plume and the atmospheric boundary layer. The models will be verified through a series of ember flight experiments conducted in a large scale boundary layer wind tunnel. The experiments will measure lofting height and downwind transport distance for a broad range of sizes, shapes, and wind conditions. This will provide experimental measurements of the flight distance for lofted embers. The experimentally verified numerical model will be used to perform parametric sensitivity studies to establish those parameters that most greatly influence the downwind risk of ember spotting and starting fire. The spot fires can cause significant property damage and can endanger the lives of home owners and firefighters. Understanding the mechanics of how embers are lofted up into the atmosphere and then blown downwind will greatly enhance our ability to predict the risk of spot fires and improve our response to such threats. The project will transform the way that ember flight is modeled by addressing the random nature of the processes involved. The ultimate goal is to mitigate property losses caused by spot fires in wildfire environment. The research team will develop a public outreach program to educate school students about the risks from wildfires, and to encourage students to pursue careers in science and engineering. The outreach program will be focused on South Carolina schools through demonstrations of the tests and videos and other materials that will be made available on the web.