firemodels · cxp484 · Aug 3, 2026 · Jul 29, 2026 · Jul 29, 2026 · Jul 30, 2026
diff --git a/Manuals/FDS_User_Guide/FDS_User_Guide.tex b/Manuals/FDS_User_Guide/FDS_User_Guide.tex
@@ -9915,6 +9915,12 @@ \subsubsection{Area Integral}
 \ee
 where $dA$ depends on the coordinates you specify for \ct{XB}. Note that this statistic is only appropriate for gas phase quantities, in particular those whose units involve \unit{\per\meter^2}. For example, the quantity \ct{'MASS FLUX X'} along with \ct{SPEC_ID='my gas'} is an appropriate output quantity if you want to know the mass flux of the gas species that you have named \ct{'my gas'} through an area normal to the $x$ direction. Note also that you must specify an area to sum over via the coordinate parameters, \ct{XB}, which can extend into multiple meshes.
 
+\subsubsection{Volume}
+
+This feature is usually used in conjunction with \ct{SPATIAL_STATISTIC='VOLUME INTEGRAL'} above (use two separate \ct{DEVC} lines, each with the same \ct{QUANTITY}). When performing precise mass and energy balances, it is useful to know exactly the volume of gas present in the region of interest. Using \ct{SPATIAL_STATISTIC='VOLUME'} produces the discrete analog of
+\be \int \; \d V \ee
+where $dV$ depends on the coordinates you specify for \ct{XB}.  
+
 \subsubsection{Area}
 
 This feature is usually used in conjunction with \ct{SPATIAL_STATISTIC='AREA INTEGRAL'} above (use two separate \ct{DEVC} lines, each with the same \ct{QUANTITY}). When performing precise mass and energy balances, it is useful to know exactly the area of \ct{VENT} or \ct{SURF} of interest. Note that this may differ slightly from what is specified in the input file due to grid snapping for Cartesian geometries or due to the approximations used to represent curvilinear geometries.  Using \ct{SPATIAL_STATISTIC='AREA'} produces the discrete analog of

diff --git a/Manuals/FDS_Validation_Guide/Plume_Chapter.tex b/Manuals/FDS_Validation_Guide/Plume_Chapter.tex
@@ -1174,6 +1174,22 @@ \section{Flame Tilt}
 \end{figure}
 
 
+\clearpage
+
+\section{Fireball Diameter}
+\label{Fireball Diameter}
+
+A fireball is caused by a sudden, violent rupture of a container containing volatile liquids or gases, typically under high pressure. Figure~\ref{Fireball_Diameter_Scatterplot} summarizes comparisons of the measured and predicted maximum horizontal fireball diameter of several sets of experiments.
+
+\begin{figure}[!h]
+\begin{center}
+\includegraphics[height=4.in]{SCRIPT_FIGURES/Scatterplots/FDS_Fireball_Diameter}
+\end{center}
+\caption[Summary of fireball diameter predictions]
+{Summary of measured and predicted maximum fireball diameter.}
+\label{Fireball_Diameter_Scatterplot}
+\end{figure}
+
 
 \clearpage
 

diff --git a/Manuals/FDS_Validation_Guide/SCRIPT_FIGURES/Sandia_Fireballs/.gitignore b/Manuals/FDS_Validation_Guide/SCRIPT_FIGURES/Sandia_Fireballs/.gitignore
diff --git a/Manuals/FDS_Validation_Guide/Species_Chapter.tex b/Manuals/FDS_Validation_Guide/Species_Chapter.tex
@@ -1869,8 +1869,73 @@ \subsection{NIST Pool Fires}
 \label{NIST_Pool_Fires_Propane_50kW}
 \end{figure}
 
+
 \clearpage
 
+\subsection{Utiskul Compartment}
+
+\begin{figure}[p]
+\begin{tabular*}{\textwidth}{l@{\extracolsep{\fill}}r}
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_HGL_Temp_Test_1} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Jet_Temp_Test_1} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_1_Pressure} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_1_Heat_Flux} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_1_O2} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_1_CO2} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_1_CO} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_1_MLR}
+\end{tabular*}
+\caption[Summary of Utiskul Compartment, Test 1]{Summary of Utiskul Compartment, Test 1.}
+\label{Utiskul_1}
+\end{figure}
+
+\begin{figure}[p]
+\begin{tabular*}{\textwidth}{l@{\extracolsep{\fill}}r}
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_HGL_Temp_Test_2} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Jet_Temp_Test_2} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_2_Pressure} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_2_Heat_Flux} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_2_O2} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_2_CO2} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_2_CO} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_2_MLR}
+\end{tabular*}
+\caption[Summary of Utiskul Compartment, Test 2]{Summary of Utiskul Compartment, Test 2.}
+\label{Utiskul_2}
+\end{figure}
+
+\begin{figure}[p]
+\begin{tabular*}{\textwidth}{l@{\extracolsep{\fill}}r}
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_HGL_Temp_Test_3} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Jet_Temp_Test_3} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_3_Pressure} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_3_Heat_Flux} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_3_O2} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_3_CO2} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_3_CO} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_3_MLR}
+\end{tabular*}
+\caption[Summary of Utiskul Compartment, Test 3]{Summary of Utiskul Compartment, Test 3.}
+\label{Utiskul_3}
+\end{figure}
+
+\begin{figure}[p]
+\begin{tabular*}{\textwidth}{l@{\extracolsep{\fill}}r}
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_HGL_Temp_Test_4} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Jet_Temp_Test_4} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_4_Pressure} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_4_Heat_Flux} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_4_O2} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_4_CO2} \\
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_4_CO} &
+\includegraphics[height=2.15in]{SCRIPT_FIGURES/Utiskul_Compartment/Utiskul_Compartment_Test_4_MLR}
+\end{tabular*}
+\caption[Summary of Utiskul Compartment, Test 4]{Summary of Utiskul Compartment, Test 4.}
+\label{Utiskul_4}
+\end{figure}
+
+
+\clearpage
 
 \subsection{Summary, Products of Incomplete Combustion}
 \label{Carbon Monoxide Concentration}

diff --git a/Source/dump.f90 b/Source/dump.f90
@@ -8105,15 +8105,27 @@ SUBROUTINE UPDATE_DEVICES_1(T,DT,NM)
 SUBROUTINE SELECT_SPATIAL_STATISTIC(OPT_LP_INDEX,OPT_CUT_FACE_INDEX)
 
 INTEGER, OPTIONAL :: OPT_LP_INDEX,OPT_CUT_FACE_INDEX
-REAL(EB) :: PWT,AREA
+REAL(EB) :: PWT,AREA,R1,R2,VOLUME
 INTEGER :: ICF,JCF,NFACE
 
 PWT = 1._EB
 IF (PRESENT(OPT_LP_INDEX)) PWT = LAGRANGIAN_PARTICLE(OPT_LP_INDEX)%PWT
 
 AREA = B1%AREA
-IF (TWO_D) AREA = AREA/DY(BC%JJG)
-IF (CYLINDRICAL) AREA = AREA*2._EB*PI
+IF (TWO_D) THEN
+   AREA = AREA/DY(BC%JJG)
+   VOLUME = DX(BC%IIG)*DZ(BC%KKG)
+ELSEIF(CYLINDRICAL) THEN
+   R1 = R(BC%IIG-1)
+   R2 = R(BC%IIG)
+   AREA = AREA*2._EB*PI
+   VOLUME = PI*(R2**2-R1**2)*DZ(BC%KKG)
+ELSE
+   VOLUME = DX(BC%IIG)*DY(BC%JJG)*DZ(BC%KKG)
+   IF (CC_IBM) THEN
+      IF (CCVAR(BC%IIG,BC%JJG,BC%KKG,CC_IDCF) > 0) VOLUME = VOLUME * CUT_CELL(CCVAR(BC%IIG,BC%JJG,BC%KKG,CC_IDCC))%ALPHA_CC
+   ENDIF
+ENDIF
 
 IF (PRESENT(OPT_CUT_FACE_INDEX)) THEN
    ICF = OPT_CUT_FACE_INDEX
@@ -8153,6 +8165,8 @@ SUBROUTINE SELECT_SPATIAL_STATISTIC(OPT_LP_INDEX,OPT_CUT_FACE_INDEX)
          SDV%VALUE_1 = SDV%VALUE_1 + AREA*PWT
       CASE('SUM')
          SDV%VALUE_1 = SDV%VALUE_1 + VALUE
+      CASE('VOLUME')
+         SDV%VALUE_1 = SDV%VALUE_1 + VOLUME
    END SELECT
 ENDIF
 

diff --git a/Source/turb.f90 b/Source/turb.f90
@@ -1692,15 +1692,16 @@ SUBROUTINE SYNTHETIC_TURBULENCE(DT,T)
 
 USE MATH_FUNCTIONS, ONLY: EVALUATE_RAMP
 USE PHYSICAL_FUNCTIONS, ONLY: GET_WIND_AT_HEIGHT
+USE MPI_F08
 
 REAL(EB), INTENT(IN) :: DT,T
 INTEGER :: NE,NV,NT,II,JJ,KK,NM
-INTEGER :: IN,IA,IC
+INTEGER :: IN,IA,IC,IERR
 TYPE(VENTS_TYPE), POINTER :: VT
 TYPE(SURFACE_TYPE), POINTER :: SF
 REAL(EB) :: RAMP_T,TSI,SIGMA_MAX,ADV_VEL(3),SGN,UW,VW,WW,U1,V1,W1
-REAL(EB) :: U_ADD,V_ADD,W_ADD
-REAL(EB), ALLOCATABLE :: VENT_VEL(:,:)
+REAL(EB) :: U_ADD,V_ADD,W_ADD,U_MEAN
+REAL(EB), ALLOCATABLE :: VENT_VEL(:,:),VENT_MEAN_SUM(:),VENT_MEAN_CNT(:)
 LOGICAL, ALLOCATABLE :: VENT_VEL_SET(:)
 
 ! Reference:
@@ -1860,6 +1861,51 @@ SUBROUTINE SYNTHETIC_TURBULENCE(DT,T)
    ENDDO VENT_APPLY_LOOP
 ENDDO MESH_APPLY_LOOP
 
+! Subtract the vent mean of the normal component so fluctuations do not
+! change volume flow. Must be global over TOTAL_INDEX (all mesh sections) 
+! to avod jumps at mesh interfaces
+ALLOCATE(VENT_MEAN_SUM(N_VENT_TOTAL),SOURCE=0._EB)
+ALLOCATE(VENT_MEAN_CNT(N_VENT_TOTAL),SOURCE=0._EB)
+DO NM=LOWER_MESH_INDEX,UPPER_MESH_INDEX
+   CALL POINT_TO_MESH(NM)
+   DO NV=1,N_VENT
+      VT => VENTS(NV)
+      IF (VT%N_EDDY==0) CYCLE
+      NT = VT%TOTAL_INDEX
+      SELECT CASE (ABS(VT%IOR))
+         CASE(1)
+            VENT_MEAN_SUM(NT) = VENT_MEAN_SUM(NT) + SUM(VT%U_EDDY)
+            VENT_MEAN_CNT(NT) = VENT_MEAN_CNT(NT) + REAL(SIZE(VT%U_EDDY),EB)
+         CASE(2)
+            VENT_MEAN_SUM(NT) = VENT_MEAN_SUM(NT) + SUM(VT%V_EDDY)
+            VENT_MEAN_CNT(NT) = VENT_MEAN_CNT(NT) + REAL(SIZE(VT%V_EDDY),EB)
+         CASE(3)
+            VENT_MEAN_SUM(NT) = VENT_MEAN_SUM(NT) + SUM(VT%W_EDDY)
+            VENT_MEAN_CNT(NT) = VENT_MEAN_CNT(NT) + REAL(SIZE(VT%W_EDDY),EB)
+      END SELECT
+   ENDDO
+ENDDO
+IF (N_MPI_PROCESSES>1) THEN
+   CALL MPI_ALLREDUCE(MPI_IN_PLACE,VENT_MEAN_SUM,N_VENT_TOTAL,MPI_DOUBLE_PRECISION,MPI_SUM,MPI_COMM_WORLD,IERR)
+   CALL MPI_ALLREDUCE(MPI_IN_PLACE,VENT_MEAN_CNT,N_VENT_TOTAL,MPI_DOUBLE_PRECISION,MPI_SUM,MPI_COMM_WORLD,IERR)
+ENDIF
+DO NM=LOWER_MESH_INDEX,UPPER_MESH_INDEX
+   CALL POINT_TO_MESH(NM)
+   DO NV=1,N_VENT
+      VT => VENTS(NV)
+      IF (VT%N_EDDY==0) CYCLE
+      NT = VT%TOTAL_INDEX
+      IF (VENT_MEAN_CNT(NT)<=TWO_EPSILON_EB) CYCLE
+      U_MEAN = VENT_MEAN_SUM(NT)/VENT_MEAN_CNT(NT)
+      SELECT CASE (ABS(VT%IOR))
+         CASE(1); VT%U_EDDY = VT%U_EDDY - U_MEAN
+         CASE(2); VT%V_EDDY = VT%V_EDDY - U_MEAN
+         CASE(3); VT%W_EDDY = VT%W_EDDY - U_MEAN
+      END SELECT
+   ENDDO
+ENDDO
+DEALLOCATE(VENT_MEAN_SUM,VENT_MEAN_CNT)
+
 END SUBROUTINE SYNTHETIC_TURBULENCE