A Water and Energy Balance Model for Studying Temperature and Vulnerability of Complex Fuel to Ignition in Open Environments

Extreme heat sources can cause objects in their proximity to attain temperatures high enough to ignite or smolder, which can start and spread fires. Besides vicinity to heat sources, surface topography and moisture content, as well as local solar radiation and weather conditions are important factors that define the preconditioning of fuels and impact the fire spreading behavior. To the best of our knowledge, currently, there exists no model capable of simulating the temperature evolution of complex objects in connection with the diurnally variable environment to determine ignition preconditioning of fuels. This study develops a coupled water and energy balance model capable of simulating surface temperature and moisture content of multi-material objects/fuels of complex shapes in high spatial and temporal resolutions under changing environmental conditions and/or external heat sources. This coupled model considers all fundamental components of energy equilibrium (radiation, sensible and latent heat fluxes, and conduction) on the surface and at the same time determines the water content and energy budget within the material of objects or fuels. This work presents the model theory and demonstrates that the model performs well against available observations. The model can be used in various fuel condition problems and due to its high spatiotemporal resolution, can also be coupled with computational fluid dynamics simulations when coupled physics is desired.

*This work was supported by DoD SERDP RC20-1298