A Mechanism for the Formation of Transverse Horizontal Vortices on Wildland Fires

Transverse vorticies are horizontal vortices oriented perpendicular to the mean flow and are frequently observed climbing the upwind side of smoke columns. While these vortex structures have been described in the literature, little has been done to examine their fundamental dynamics or describe any potential impact on fire behavior. Using a high-resolution numerical model we investigate the atmosphere's response to an elliptical, volumetric heat source that represents an idealized wildland fire. It is hypothesized that the transverse vortex arises through the interaction near the head of the fire of hairpin vortices formed along the flanks of the fire. Evidence supporting this theory along with potential implications for fire behavior will be presented.