ERI: Understanding the Role of Non-steady Wind Gusts in Wildfire Spread

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Increased extreme fire behavior (both prevalence and severity) has caused substantial loss of property and human life, generated air pollution over large areas, and displaced large numbers of people. Accurate prediction of wildfire growth is vital for fire response (firefighting and evacuations) as well as preventative measures (prescribed burning and community hardening). This project seeks to better defend against these negative consequences of wildfires by better understanding the role of non-steady wind on their growth. Two physical mechanisms for fire growth are studied: flame-driven fire spread and firebrand spotting. Flame-driven fire spread is the process by which flames heat and ignite nearby fuel and firebrand spotting is the process by which burning debris (firebrands) are transported by the wind and fire gases to fuels which they may ignite. Nearly all prior fundamental studies of these processes have focused on fire behavior under steady conditions and have ignored the role of non-steady wind such as gusts. For firebrand generation from burning vegetation, the role of wind is known to be important, but it has not been fully characterized. This project examines whether fire spread and firebrand generation behavior can be explained with steady-flow results or if non-steady wind produces more extreme fire behavior. During the project, educational modules on wildfire topics related to the research will be incorporated into one graduate and one undergraduate course. Through these modules and student involvement in the research the PI will help prepare an engineering workforce knowledgeable about wildland and wildland-urban interface fire and cultivate interest in these areas of Fire Protection Engineering.This project will examine the physical mechanisms by which non-steady wind interacts with wildfire behavior, specifically flame-driven wildfire spread and firebrand spotting, while also making novel measurements of these wildfire behaviors using imaging methods. The motivation for the project is to facilitate improvement of physical modelling of wildfire spread. Current models do not accurately predict fire spread in all situations. Wind strongly influences wildfire spread through intermittent convective heating of fine fuel particles while also contributing to firebrand spotting. The role of transient wind (i.e., gusts) has not been examined in these models. The project addresses research needs identified by the community for firebrand spotting using new experimental methodologies to characterize firebrand generation and more comprehensive characterization of wildfire spread to enable verifiable modelling of wildfire spread to address the gap between prediction with current models and observed behavior.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.