Preliminary Analysis of Slope and Fuel Bed Effect on Jump Behavior in Forest Fires

Abstract

The merging of two linear forest fire fronts intersecting at a small angle creates an acceleratin fire that is designated as “jump fire”, given the very high value of the rate of spread that it can reach in a relatively short time. The analysis of the intersection point of the fire lines is of particular relevance to assess jump fire properties. It is found that the displacement velocity of this point increases i a short time, reaching values that are not commonly found in normal fire behavior and allow the inclusion of this type of fire in the category of extreme fire behavior. The distance travelled in the acceleration phase and the maximum velocity reached increase with slope angle. Tests performed with three different fuels in laboratory conditions showed that for a given combination of fuel bed slope and initial angle between fire lines, the non-dimensional values of those two parameters are practically constant.