firemodels · ericvmueller · Aug 10, 2026 · Aug 10, 2026
diff --git a/Manuals/FDS_User_Guide/FDS_User_Guide.tex b/Manuals/FDS_User_Guide/FDS_User_Guide.tex
@@ -7759,7 +7759,7 @@ \section{Level Set Model for Wildland Fire Spread}
 \end{lstlisting}
 \ct{VEG_LSET_ROS_00} is the no-wind, no-slope rate of spread for the given fuel model. \ct{VEG_LSET_SIGMA} (\unit{\per\meter}) and \ct{VEG_LSET_BETA} are the average surface-to-volume ratio ($\sigma$) and packing ratio ($\beta$) of the underlying vegetation. \ct{VEG_LSET_HT} (m) is the height of the vegetation. When the fire front arrives at a given surface cell, fuel vapors are generated at a rate given by
 \be
-\dot{m}_{\rm f}'' = (1-\nu_{\rm char}) \frac{m_{\rm f}''}{\delta t} \; {\rm kg}/({\rm m}^2 \cdot {\rm s})  \quad ; \quad \delta t = \frac{75600}{\sigma} \; \unit{s}
+\dot{m}_{\rm f}'' = (1-\nu_{\rm char}) \frac{m_{\rm f}''}{\delta t} \; {\rm kg}/({\rm m}^2 \cdot {\rm s})  \quad ; \quad \delta t = \frac{75600}{\sigma} \; \unit{s} \label{eq:ls_mlr}
 \ee
 Here, $m_{\rm f}''$ is the dry fuel loading in units of \unit{kg/m^2} (\ct{VEG_LSET_SURF_LOAD}, default 1.0~\unit{kg/m^2}); $\nu_{\rm char}$ is the char fraction (\ct{VEG_LSET_CHAR_FRACTION}, default 0.2); and $\delta t$ is the duration of the fire at a given location. The expression for the burn duration is given by Albini~\cite{Albini:1976}, but you can enter your own burn duration using \ct{VEG_LSET_FIREBASE_TIME} (s).
 
@@ -7848,7 +7848,7 @@ \subsubsection{Examples of Uncoupled Level Set Calculations}
 \subsubsection{Examples of Coupled Level Set Calculations}
 \label{level_set_fuel_model_1}
 
-In this example, \ct{WUI/level_set_fuel_model_1.fds}, a fire is ignited directly in the center of a square patch of flat terrain, $L=1000$~m on a side, with no wind. \ct{VEG_LSET_FUEL_INDEX=1} (Short Grass) is selected as the vegetation type. The simulation is performed on a uniform mesh with $\dx=25$~m grid cells. For this type of vegetation, the mass loss rate is calculated to be $\dot{m}''=0.00955$~\unit{kg/m^2.s}, the heat of combustion is assumed to be $\Delta H=18607$~kJ/kg, and the local duration of burning is calculated to be $\Delta t=6.584$~s. These values are all reported in the file \ct{level_set_fuel_model_1.out}. After 10~h of simulation, the fire sweeps over the entire domain, consuming $\dot{m}'' L^2 \Delta t \approx 62877$~kg of vegetation. The left hand side of Fig.~\ref{level_set_fuel_model_1_fig} displays the fire intensity (burning rate) after 5~h, and the right hand side displays the integrated mass loss. Note that in this case the rate of spread is ${\rm ROS} \approx 0.03$~m/s, which means that the fire front crosses a single grid cell in approximately $\dx/{\rm ROS} \approx 830$~s, a much greater time period than the vegetation burning time, $\Delta t$. To ensure a relatively smooth fire front and burning rate, the mass loss rate and burning duration are adjusted by dividing and multiplying these values, respectively, by $\dx/{\rm ROS}$.
+In this example, \ct{WUI/level_set_fuel_model_1.fds}, a fire is ignited directly in the center of a square patch of flat terrain, $L=1000$~m on a side, with no wind and a uniform mesh with $\dx=25$~m grid cells. \ct{VEG_LSET_FUEL_INDEX=1} (Short Grass) is selected as the vegetation type. For this type of vegetation, the fuel load is $m''=0.1659$~\unit{kg/m^2} and the burning rate is determined from Eq.~\ref{eq:ls_mlr} (with a burning duration of $\Delta t=6.584$~s). These values are all reported in the file \ct{level_set_fuel_model_1.out}. Given the default char yield of 0.2, the total mass consumed after the fire has spread over the full domain should be $(1-\nu_{\rm char}) m'' L^2 \approx 132720$~kg. The left hand side of Fig.~\ref{level_set_fuel_model_1_fig} displays the fire intensity (burning rate) after 5~h, and the right hand side displays the integrated mass loss. Note that in this case the rate of spread is ${\rm ROS} \approx 0.03$~m/s, which means that the fire front crosses a single grid cell in approximately $\dx/{\rm ROS} \approx 830$~s, a much greater time period than the vegetation burning time, $\Delta t$. To ensure a relatively smooth fire front and burning rate, the mass loss rate and burning duration are adjusted following a mass conserving scheme described in the FDS Technical Reference Guide~\cite{FDS_Math_Guide}.
 
 \begin{figure}[ht]
     \includegraphics[trim=.5in 0 .5in 0, clip, height=2.4in]{SCRIPT_FIGURES/level_set_fuel_model_1.png}

diff --git a/Utilities/Python/FDS_verification_dataplot_inputs.csv b/Utilities/Python/FDS_verification_dataplot_inputs.csv
@@ -471,7 +471,7 @@ d,leak_test_2,HVAC/leak_test_2_git.txt,HVAC/leak_test_2.csv,1,2,Time,pres_1|pres
 d,leak_test_3,HVAC/leak_test_3_git.txt,HVAC/leak_test_3.csv,1,2,Time,p1|p2,Ideal (p1)|Ideal (p2),ko|ro,0,100000,,0,100000,-1.00E+09,1.00E+09,0,HVAC/leak_test_3_devc.csv,2,3,Time,p1|p2,FDS (p1)|FDS (p2),k-|r-,0,100000,,0,100000,-1.00E+09,1.00E+09,0,Pressure (leak_test_3) (OBST),Time (s),Pressure (Pa),0,30,1,0,600,1,no,0.05 0.90,SouthEast,,1,linear,FDS_Verification_Guide/SCRIPT_FIGURES/leak_test_3_obst,Relative Error,end,0.01,HVAC,ms,m,TeX
 d,leak_test_3,HVAC/leak_test_3_git.txt,HVAC/leak_test_3.csv,1,2,Time,p1|p2,Ideal (p3)|Ideal (p4),ko|ro,0,100000,,0,100000,-1.00E+09,1.00E+09,0,HVAC/leak_test_3_devc.csv,2,3,Time,p3|p4,FDS (p3)|FDS (p4),k-|r-,0,100000,,0,100000,-1.00E+09,1.00E+09,0,Pressure (leak_test_3) (GEOM),Time (s),Pressure (Pa),0,30,1,0,600,1,no,0.05 0.90,SouthEast,,1,linear,FDS_Verification_Guide/SCRIPT_FIGURES/leak_test_3_geom,Relative Error,end,0.01,HVAC,ms,m,TeX
 d,leak_test_4,HVAC/leak_test_4_git.txt,HVAC/leak_test_4.csv,1,2,Time,p,Ideal,ko,0,100000,,0,100000,-1.00E+09,1.00E+09,0,HVAC/leak_test_4_devc.csv,2,3,Time,p1,FDS,k-,0,100000,,0,100000,-1.00E+09,1.00E+09,0,Pressure (leak_test_4),Time (s),Pressure (Pa),0,30,1,0,500,1,no,0.05 0.90,SouthEast,,1,linear,FDS_Verification_Guide/SCRIPT_FIGURES/leak_test_4,Relative Error,end,0.05,HVAC,ms,m,TeX
-d,level_set_fuel_model_1,WUI/level_set_fuel_model_1_git.txt,WUI/level_set_fuel_model_1.csv,1,2,Time,mass,Expected,ko,0,400000,,0,400000,-1.00E+09,1.00E+09,0,WUI/level_set_fuel_model_1_devc.csv,2,3,Time,mass,FDS,k-,0,400000,,0,400000,-1.00E+09,1.00E+09,0,Mass Loss (level_set_fuel_model_1),Time (h),Mass (kg),0,10,3600,0,100000,1,no,0.05 0.90,SouthEast,,1,linear,FDS_User_Guide/SCRIPT_FIGURES/level_set_fuel_model_1_mass,Relative Error,end,0.01,WUI,g^,g,TeX
+d,level_set_fuel_model_1,WUI/level_set_fuel_model_1_git.txt,WUI/level_set_fuel_model_1.csv,1,2,Time,mass,Expected,ko,0,400000,,0,400000,-1.00E+09,1.00E+09,0,WUI/level_set_fuel_model_1_devc.csv,2,3,Time,mass,FDS,k-,0,400000,,0,400000,-1.00E+09,1.00E+09,0,Mass Loss (level_set_fuel_model_1),Time (h),Mass (kg),0,10,3600,0,220000,1,no,0.05 0.90,SouthEast,,1,linear,FDS_User_Guide/SCRIPT_FIGURES/level_set_fuel_model_1_mass,Relative Error,end,0.01,WUI,g^,g,TeX
 d,liquid_mixture,Pyrolysis/liquid_mixture_git.txt,Pyrolysis/liquid_mixture.csv,1,2,Time,Fuel Mass|Water Mass,Expected Fuel Mass| Expected Water Mass,ko|ro,0,400000,,0,400000,-1.00E+09,1.00E+09,0,Pyrolysis/liquid_mixture_mass.csv,2,3,Time,N-HEXANE|WATER VAPOR,FDS (N-HEXANE)|FDS (WATER VAPOR),k-|r-,0,400000,,0,400000,-1.00E+09,1.00E+09,0,Evaporated Mass (liquid_mixture),Time (s),Mass (kg),0,600,1,0,1.5,1,no,0.05 0.90,East,,1,linear,FDS_User_Guide/SCRIPT_FIGURES/liquid_mixture,Relative Error,end,0.01,WUI,g^,g,TeX
 d,LS_wind_ramp,WUI/LS_wind_ramp_lin_git.txt,WUI/LS_wind_ramp.csv,1,2,U,R_lin,Exact (linear),ko,0,400000,,0,400000,-1.00E+09,1.00E+09,0,WUI/LS_wind_ramp_lin_devc.csv,2,3,U,R,FDS (linear),kx,0,400000,,0,400000,-1.00E+09,1.00E+09,0,LS Wind Ramp (LS_wind_ramp),U (m/s),R (m/s),0,5,1,0.02,0.12,1,no,0.05 0.90,West,,1,linear,FDS_Verification_Guide/SCRIPT_FIGURES/LS_wind_ramp,Relative Error,mean,0.05,WUI,g^,g,TeX
 f,LS_wind_ramp,WUI/LS_wind_ramp_lin_git.txt,WUI/LS_wind_ramp.csv,1,2,U,R_quad,Exact (quadratic),ro,0,400000,,0,400000,-1.00E+09,1.00E+09,0,WUI/LS_wind_ramp_quad_devc.csv,2,3,U,R,FDS (quadratic),rx,0,400000,,0,400000,-1.00E+09,1.00E+09,0,LS Wind Ramp (LS_wind_ramp),U (m/s),R (m/s),0,5,1,0.02,0.12,1,no,0.05 0.90,West,,1,linear,FDS_Verification_Guide/SCRIPT_FIGURES/LS_wind_ramp,Relative Error,mean,0.05,WUI,g^,g,TeX
@@ -852,4 +852,4 @@ d,rms_cov_corr,Controls/rms_cov_corr_git.txt,Controls/rms_cov_corr.csv,1,2,Time,
 d,rms_cov_corr,Controls/rms_cov_corr_git.txt,Controls/rms_cov_corr.csv,1,2,Time,uwcov,Analytic,k-,0,100000,,0,100000,-1.00E+09,1.00E+09,0,Controls/rms_cov_corr_devc.csv,2,3,Time,U-W COV,FDS,r-,0,100000,,0,100000,-1.00E+09,1.00E+09,0,U-W COV  (rms_cov_cor),Time (s),$uw$ covariance (m²/s²),0,1000,1,-0.15,0.15,1,no,0.05 0.90,SouthEast,,1,linear,FDS_Verification_Guide/SCRIPT_FIGURES/rms_cov_corr_cov,Relative Error,end,0.02,rmscovcorr,yd,b,TeX
 d,rms_cov_corr,Controls/rms_cov_corr_git.txt,Controls/rms_cov_corr.csv,1,2,Time,uwcorr,Analytic,k-,0,100000,,0,100000,-1.00E+09,1.00E+09,0,Controls/rms_cov_corr_devc.csv,2,3,Time,U-W CORR,FDS,r-,0,100000,,0,100000,-1.00E+09,1.00E+09,0,U-W CORR  (rms_cov_cor),Time (s),$uw$ cross correlation,0,1000,1,-1,1,1,no,0.05 0.90,SouthEast,,1,linear,FDS_Verification_Guide/SCRIPT_FIGURES/rms_cov_corr_corr,Relative Error,end,0.02,rmscovcorr,yd,b,TeX
 s,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
-d,flux_time,Fires/ftp_git.txt,Fires/ftp.csv,1,2,Time,FTP|Q,Ideal FTP|Ideal Q,ko|ro,0,100000,,0,100000,-1.00E+09,1.00E+09,0,Fires/ftp_devc.csv,2,3,Time,FTP|Q,FDS FTP|FDS Q,k-|r-,0,100000,,0,100000,-1.00E+09,1.00E+09,0,Flux-Time Product,Time (s),FTP (kJ/m²) or Q (kJ),0,10,1,0,2000,1,no,0.05 0.90,West,,1,linear,FDS_User_Guide/SCRIPT_FIGURES/ftp,Relative Error,end,0.02,ftp,md,m,TeX
+d,flux_time,Fires/ftp_git.txt,Fires/ftp.csv,1,2,Time,FTP|Q,Ideal FTP|Ideal Q,ko|ro,0,100000,,0,100000,-1.00E+09,1.00E+09,0,Fires/ftp_devc.csv,2,3,Time,FTP|Q,FDS FTP|FDS Q,k-|r-,0,100000,,0,100000,-1.00E+09,1.00E+09,0,Flux-Time Product,Time (s),FTP (kJ/m²) or Q (kJ),0,10,1,0,2000,1,no,0.05 0.90,West,,1,linear,FDS_User_Guide/SCRIPT_FIGURES/ftp,Relative Error,end,0.02,ftp,md,m,TeX