LIHTFire: A high-resolution 1D physics-based wildfire spread model

We describe the development and performance of a dynamical one-dimensional (1D) model of fire spread (LIHTFire, Linear Ignition and Heat Transfer). The model resolves burning rates, heat transfer, and ignition at cm-scales with explicit accounting of heterogeneous fuels and time-varying weather. An empirical convective heating method speeds computation compared to CFD methods. Heating, drying, pyrolysis, ignition, and solid phase combustion of fuel with varying sizes and shapes is represented by a particle model that captures within-particle gradients. The heat transfer, burning behaviors, and fire spread characteristics (spread rate, flame length, and flame zone depth) are compared with experiments of particle heating and fire behaviors from laboratory and field studies. The 1D model rapidly simulates spreading line fires over domains of ~102 m and reveals strong coupling of physical processes involved in producing fire spread, spread thresholds, and non-steady and nonlinear behaviors including acceleration and damped oscillation. The model is intended for generalized use in wildland fire spread predictions, either as a stand-alone simulation for understanding the interplay of fire and environmental conditions but also for use in 2D and 3Dsimulation systems.