WIP: fieldStatistics: add volume-weighted average to the options

src/functionObjects/field/fieldStatistics/fieldStatistics.C

@@ -50,6 +50,16 @@ Foam::functionObjects::fieldStatistics::modeTypeNames_
     { modeType::mdCmpt, "component" },
 });
 
+const Foam::Enum
+<
+    Foam::functionObjects::fieldStatistics::meanType
+>
+Foam::functionObjects::fieldStatistics::meanTypeNames_
+({
+    { meanType::ARITHMETIC, "arithmetic" },
+    { meanType::VOLUMETRIC, "volumetric" },
+});
+
 
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
@@ -156,6 +166,7 @@ bool Foam::functionObjects::fieldStatistics::read(const dictionary& dict)
     internal_ = dict.getOrDefault("internal", false);
 
     mode_ = modeTypeNames_.getOrDefault("mode", dict, modeType::mdMag);
+    mean_ = meanTypeNames_.getOrDefault("mean", dict, meanType::ARITHMETIC);
 
     // Reset and reprepare the input field names
     fieldSet_.clear();

src/functionObjects/field/fieldStatistics/fieldStatistics.H

@@ -53,6 +53,7 @@ Usage
         // Optional entries
         mode             <word>;
         internal         <bool>;
+        mean             <word>;
 
         // Inherited entries
         ...
@@ -69,6 +70,7 @@ Usage
       mode   | Output format of the statistical results | word | no | magnitude
       internal | Flag to use internal fields only in computing statistics <!--
                -->                                      | bool | no | false
+      mean     | Type of the mean operation             | word | no | arithmetic
     \endtable
 
     Available statistics of the operand field through the \c statistics entry:
@@ -85,6 +87,12 @@ Usage
       component  | Output statistics separately for each component
     \endverbatim
 
+    Options for the \c meanType entry:
+    \verbatim
+      arithmetic  | Arithmetic mean (average)
+      volumetric  | Volume-weighted arithmetic mean
+    \endverbatim
+
     The inherited entries are elaborated in:
       - \link functionObject.H \endlink
       - \link writeFile.H \endlink
@@ -133,6 +141,17 @@ class fieldStatistics
         static const Enum<modeType> modeTypeNames_;
 
 
+        //- Options for the mean type of the specified fields
+        enum meanType : char
+        {
+            ARITHMETIC = 0,  //!< "Arithmetic mean (average)"
+            VOLUMETRIC       //!< "Volume-weighted arithmetic mean"
+        };
+
+        //- Names for meanType
+        static const Enum<meanType> meanTypeNames_;
+
+
     // Private Classes
 
         //- Type-safe union for input field types
@@ -172,6 +191,9 @@ class fieldStatistics
         //- Output-format mode - only applicable for tensor ranks > 0
         modeType mode_;
 
+        //- Type of the mean of the specified fields
+        meanType mean_;
+
         //- Operand fields on which statistics are computed
         volFieldSelection fieldSet_;
 

src/functionObjects/field/fieldStatistics/fieldStatisticsTemplates.C

@@ -108,6 +108,12 @@ bool Foam::functionObjects::fieldStatistics::calcStat(const word& fieldName)
 template<class T>
 T Foam::functionObjects::fieldStatistics::calcMean(const Field<T>& field)
 {
+    if (internal_ && (mean_ == VOLUMETRIC))
+    {
+        const auto& V = mesh_.V();
+        return (gSum(V*field)/gSum(V));
+    }
+
     return gAverage(field);
 }