Linking Empirical Data and Numerical Simulation to Characterize Dynamic Fire Behavior Associated With Interacting Firelines

Author

Marta Sergeevna JerebetsFollow

Year of Award

2025

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Forestry

Department or School/College

W.A. Franke College of Forestry

Committee Chair

Dr. Carl Seielstad

Commitee Members

Dr. Jesse Johnson, Dr. Chris Moran

Keywords

fire behavior, junction fire, simulation, fire modeling, FDS, UAS

Subject Categories

Applied Statistics | Fluid Dynamics | Forest Management | Natural Resources and Conservation | Natural Resources Management and Policy | Numerical Analysis and Scientific Computing | Other Forestry and Forest Sciences

Abstract

Understanding fuel pattern-fire process relationships is key for predicting fire behavior and effects with follow-on benefits to proactive fire management and model validation. To characterize dynamic fire behavior, this thesis leverages empirical data and numerical simulation through two complementary studies.

In the first study, longwave thermal sensors aboard unmanned aerial systems (UAS) were used to capture fine-scale fire behavior in two experimental grass burns. A novel paired design was used to quantify the effects of fuel arrangement on fire behavior with 3.66 m diameter treatments cut to a height of 0.15 m. The treatments ephemerally reduced fire rate of spread and radiative output by 15.9% and 7.1% in the two fires, respectively. 38% of treatments (54% with steady state fire behavior) formed junction fires, or two firelines coming together at an angle. These junctions temporarily intensified fire behavior, increasing peak fire radiative flux density by up to 52%, but the fireline quickly reformed, negating any lasting effect. Initial results from the Fire Dynamics Simulator (FDS), demonstrated consistency with field observations, supporting its utility in further exploring fire-fuel interactions in the modeling domain.

The second study used FDS to isolate the effects of ignition pattern, wind speed, and ignition length in homogeneous grass fuels to understand some of the controls on energy redistribution associated with junction fires compared to straight-line ignitions. Differences in fire behavior along the axis of symmetry and two adjacent transects were evaluated using peak and total heat release rate per unit volume (HRRPUV), HRRPUV over time, and spatial heat distribution. Peak HRRPUV values were 65% higher and total HRRPUV values 78% higher along the center transect, on average, for junction fires. Junction fires reached peak intensity earlier and produced consistently larger cross-sectional areas and higher projections of critical temperatures. They averaged 34% greater area affected and 21% higher temperature projections, raising potential scorch heights by an average of five meters.

These findings enhance our understanding of junction fire dynamics and demonstrate the value of integrating field data with numerical modeling. The results have practical implications for predicting canopy scorch, optimizing prescribed fire techniques, and informing fire management.

Recommended Citation

Jerebets, Marta Sergeevna, "Linking Empirical Data and Numerical Simulation to Characterize Dynamic Fire Behavior Associated With Interacting Firelines" (2025). Graduate Student Theses, Dissertations, & Professional Papers. 12525.
https://scholarworks.umt.edu/etd/12525