Merge pull request #14413 from johodges/unfreeze

FDS Source and FDS_User_Guide Add UNFREEZE_TIME parameter

Author: marcosvanella

Manuals/FDS_User_Guide/FDS_User_Guide.tex

@@ -9259,6 +9259,11 @@ \subsection*{Reading the Fields}
 \end{lstlisting}
 and FDS will read, for example, \ct{CHID_uvw_t1_m1.csv} through \ct{CHID_uvw_t1_m16.csv} in the order of the \ct{MESH} lines (note that a \ct{MULT} line for the meshes may also be used).
 
+\section{Unfreezing the Initial Flow Field}
+\label{info:FREZ}
+
+It may be useful to allow the solid phase to respond to an established flow field at the start of a simulation.  This could be accomplished with the normal restart functionality; however, this limits the number of changes that can be made to the model before a restart is made.  The \ct{UNFREEZE_TIME} parameter on the \ct{MISC} line can be used for this purpose. When set, the initial flow field is frozen with the options \ct{FREEZE_VELOCITY} and \ct{SOLID_PHASE_ONLY} set until the simulation time exceeds \ct{UNFREEZE_TIME}.
+
 
 \section{Gravity}
 \label{info:GVEC}
@@ -12731,6 +12736,7 @@ \section{\texorpdfstring{{\tt MISC}}{MISC} (Miscellaneous Parameters)}
 \ct{TMPA}                                          & Real         & Section~\ref{info:MISC_Basics}          & $^\circ$C  & 20.               \\ \hline
 \ct{TURBULENCE_MODEL}                             & Character    & Section~\ref{info:LES}                  &            & \ct{'DEARDORFF'} \\ \hline
 \ct{TURBULENT_DEPOSITION}                         & Logical      & Section~\ref{info:deposition}           &            & \ct{T}           \\ \hline
+\ct{UNFREEZE_TIME}                               & Real          & Section~\ref{info:FREZ}                 &            &                  \\ \hline
 \ct{VERBOSE}                                       & Logical      & Section~\ref{info:multimesh}            &            &                   \\ \hline
 \ct{VISIBILITY_FACTOR}                            & Real         & Section~\ref{info:visibility}           &            & 3                 \\ \hline
 \ct{VN_MAX}                                       & Real         & Section~\ref{info:VN}                   &            & 1.0               \\ \hline

Source/cons.f90

@@ -394,6 +394,7 @@ MODULE GLOBAL_CONSTANTS
 REAL(EB) :: DT_END_MINIMUM=TWO_EPSILON_EB                   !< Smallest possible final time step (s)
 REAL(EB) :: DT_END_FILL=1.E-6_EB
 INTEGER  :: DIAGNOSTICS_INTERVAL                            !< Number of time steps between diagnostic outputs
+REAL(EB) :: UNFREEZE_TIME                                   !< Time to unfreeze a simulation
 
 ! Combustion parameters
 

Source/main.f90

@@ -532,6 +532,11 @@ PROGRAM FDS
 
 INITIALIZATION_PHASE = .FALSE.
 
+IF (UNFREEZE_TIME > 0._EB) THEN 
+   FREEZE_VELOCITY=.TRUE. 
+   SOLID_PHASE_ONLY=.TRUE.
+ENDIF
+
 IF (MY_RANK==0 .AND. VERBOSE) CALL VERBOSE_PRINTOUT('Starting the time-stepping')
 
 !***********************************************************************************************************************************
@@ -569,6 +574,11 @@ PROGRAM FDS
    LO10 = INT(LOG10(REAL(MAX(1,ABS(ICYC)),EB)))
    IF (MOD(ICYC,10**LO10)==0 .OR. MOD(ICYC,DIAGNOSTICS_INTERVAL)==0 .OR. (T+DT)>=T_END) DIAGNOSTICS = .TRUE.
 
+   IF ((UNFREEZE_TIME > 0._EB).AND.(T>UNFREEZE_TIME)) THEN 
+      FREEZE_VELOCITY=.FALSE.
+      SOLID_PHASE_ONLY=.FALSE.
+   ENDIF
+
    !================================================================================================================================
    !                                           Start of Predictor part of time step
    !================================================================================================================================

Source/read.f90

@@ -1746,7 +1746,7 @@ SUBROUTINE READ_MISC
                 RND_SEED,SIMULATION_MODE,SMOKE_ALBEDO,SOLID_PHASE_ONLY,SOOT_DENSITY,SOOT_OXIDATION,&
                 TAU_DEFAULT,TENSOR_DIFFUSIVITY,TERRAIN_IMAGE,TEST_NEW_CHAR_MODEL,TEXTURE_ORIGIN,&
                 THERMOPHORETIC_DEPOSITION,THERMOPHORETIC_SETTLING,THICKEN_OBSTRUCTIONS,&
-                TMPA,TURBULENCE_MODEL,TURBULENT_DEPOSITION,UVW_FILE,&
+                TMPA,TURBULENCE_MODEL,TURBULENT_DEPOSITION,UVW_FILE,UNFREEZE_TIME,&
                 VERBOSE,VISIBILITY_FACTOR,VN_MAX,VN_MIN,Y_CO2_INFTY,Y_O2_INFTY,&
                 RADIATION,STRATIFICATION,SUPPRESSION
 
@@ -1800,6 +1800,7 @@ SUBROUTINE READ_MISC
 MAX_LEAK_PATHS       = 200
 FLUX_LIMITER         = 'null'
 LES_FILTER_TYPE      = 'null'
+UNFREEZE_TIME        = -1._EB
 
 ! Initial read of the MISC line