Merge pull request #3761 from rmcdermo/development

FDS User Guide: add section on RAMP_CHI_R Former-commit-id: 20e1dbd70ef4ccdfdc4b3b62b8e45cf2b440ab03 [formerly f15aec490e10946330a2d633eea15071d1a343e2] Former-commit-id: 1cdf728aaad32462943ae100d47cf0015f149a90 Former-commit-id: 26b0a35
firemodels · Apr 5, 2016 · 06a63c8 · 06a63c8
2 parents 00fc14c + ea6b6d0
commit 06a63c8
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diff --git a/Manuals/FDS_User_Guide/FDS_User_Guide.tex b/Manuals/FDS_User_Guide/FDS_User_Guide.tex
@@ -5341,6 +5341,17 @@ \subsection{Radiative Fraction}
 
 If multiple fuels are present, e.g., one fuel for cardboard and one fuel for polystyrene combustion, then the radiant fraction will be computed locally as reaction-weighted value, similar to the approach described by Gupta et al.~\cite{Gupta:2015}. For example, if the two fuels are 20\% and 40\% radiative fraction with, respectively, 80\% and 20\% of the heat in a grid cell, $\chi_{\rm r}$ would be $0.8 \times 0.2 + 0.2 \times 0.4 = 0.24$. Thus, $\chi_{\rm r}$ will vary in space and time.
 
+\paragraph{Time variation of radiative fraction}
+
+Even for a single fuel species the global flame radiative fraction may depend on other parameters of the problem like global equivalent ratio.  If a time variation of the radiative fraction is necessary, it may be added through a ramp function, {\ct RAMP\_CHI\_R}, on the {\ct REAC} line.
+
+\begin{lstlisting}
+&REAC ..., RADIATIVE_FRACTION = 0.23, RAMP_CHI_R = 'chi_r'/
+&RAMP ID = 'chi_r', T =  0.0, F = 1.0/
+&RAMP ID = 'chi_r', T =  5.0, F = 1.0/
+&RAMP ID = 'chi_r', T = 60.0, F = 0.1/
+\end{lstlisting}
+
 \subsection{Spatial and Temporal Resolution of the Radiation Transport Equation}
 
 \label{info:RADI_Resolution}
@@ -9336,6 +9347,7 @@ \section{\texorpdfstring{{\tt REAC}}{REAC} (Reaction Parameters)}
 {\ct O}                                   & Real        & Section~\ref{info:simple_chemistry}       &                   & 0    \\ \hline
 %{\ct ODE\_SOLVER}                         & Character   & Section~\ref??}                           &                   &       \\ \hline
 {\ct RADIATIVE\_FRACTION}                  & Real       & Section~\ref{info:CHI_R}                   &                   &                \\ \hline
+{\ct RAMP\_CHI\_R}                        & Character   & Section~\ref{info:CHI_R}                   &                   &                \\ \hline
 {\ct REAC\_ATOM\_ERROR}                   & Real        & Section~\ref{info:REAC_Diagnostics}       & atoms             & 1.E-5    \\ \hline
 {\ct REAC\_MASS\_ERROR}                   & Real        & Section~\ref{info:REAC_Diagnostics}       & kg/kg             & 1.E-4    \\ \hline
 {\ct SOOT\_H\_FRACTION}                   & Real        & Section~\ref{info:simple_chemistry}       &                   & 0.1    \\ \hline