ENH: improve volRegion handling of moving meshes (#1194)

- implemented as lazy evaluation with an additional update() method.
  This avoids unnecessary changes until the values are actually
  required.

- apply mesh motion changes for momentum, volFieldValue,
  specieReactionRates function objects

src/finiteVolume/functionObjects/volRegion/volRegion.C

@@ -109,6 +109,8 @@ void Foam::functionObjects::volRegion::calculateCache()
             << "    Region has no cells"
             << exit(FatalError);
     }
+
+    requireUpdate_ = false;
 }
 
 
@@ -137,6 +139,7 @@ Foam::functionObjects::volRegion::volRegion
 )
 :
     volMesh_(mesh),
+    requireUpdate_(true),
     cellIds_(),
     nCells_(0),
     V_(Zero),
@@ -158,10 +161,7 @@ Foam::functionObjects::volRegion::volRegion
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-bool Foam::functionObjects::volRegion::read
-(
-    const dictionary& dict
-)
+bool Foam::functionObjects::volRegion::read(const dictionary& dict)
 {
     switch (regionType_)
     {
@@ -195,6 +195,15 @@ bool Foam::functionObjects::volRegion::read
 
 const Foam::labelList& Foam::functionObjects::volRegion::cellIDs() const
 {
+    #ifdef FULLDEBUG
+    if (requireUpdate_)
+    {
+        FatalErrorInFunction
+            << "Retrieving cached values that are not up-to-date" << nl
+            << exit(FatalError);
+    }
+    #endif
+
     switch (regionType_)
     {
         case vrtCellSet:
@@ -213,15 +222,27 @@ const Foam::labelList& Foam::functionObjects::volRegion::cellIDs() const
 }
 
 
+bool Foam::functionObjects::volRegion::update()
+{
+    if (requireUpdate_)
+    {
+        calculateCache();
+        return true;
+    }
+
+    return false;
+}
+
+
 void Foam::functionObjects::volRegion::updateMesh(const mapPolyMesh&)
 {
-    calculateCache();
+    requireUpdate_ = true;
 }
 
 
 void Foam::functionObjects::volRegion::movePoints(const polyMesh&)
 {
-    calculateCache();
+    requireUpdate_ = true;
 }
 
 

src/finiteVolume/functionObjects/volRegion/volRegion.H

@@ -30,6 +30,11 @@ Group
 Description
     Volume (cell) region selection class.
 
+    The adjustments for mesh changes have been implemented with a lazy
+    evaluation, to avoid unnecessary recalculation until the values are
+    actually required. The update() method is used to ensure the cache
+    values are up-to-date.
+
     Examples of function object specification:
     \verbatim
     volRegion0
@@ -96,6 +101,9 @@ class volRegion
 
         const fvMesh& volMesh_;
 
+        //- Flag to indicate whether the volRegion requires updating
+        bool requireUpdate_;
+
         //- The cell ids, from cellSet
         labelList cellIds_;
 
@@ -178,6 +186,10 @@ public:
         //- Return total volume of the selected region
         inline scalar V() const;
 
+        //- Update the cached values as required
+        //  \return False if the values were already up to date
+        bool update();
+
 
         //- Read from dictionary
         virtual bool read(const dictionary& dict);

src/finiteVolume/functionObjects/volRegion/volRegionI.H

@@ -28,18 +28,45 @@ License
 inline const Foam::functionObjects::volRegion::regionTypes&
 Foam::functionObjects::volRegion::regionType() const
 {
+    #ifdef FULLDEBUG
+    if (requireUpdate_)
+    {
+        FatalErrorInFunction
+            << "Retrieving cached values that are not up-to-date" << nl
+            << exit(FatalError);
+    }
+    #endif
+
     return regionType_;
 }
 
 
 inline Foam::label Foam::functionObjects::volRegion::nCells() const
 {
+    #ifdef FULLDEBUG
+    if (requireUpdate_)
+    {
+        FatalErrorInFunction
+            << "Retrieving cached values that are not up-to-date" << nl
+            << exit(FatalError);
+    }
+    #endif
+
     return nCells_;
 }
 
 
 inline Foam::scalar Foam::functionObjects::volRegion::V() const
 {
+    #ifdef FULLDEBUG
+    if (requireUpdate_)
+    {
+        FatalErrorInFunction
+            << "Retrieving cached values that are not up-to-date" << nl
+            << exit(FatalError);
+    }
+    #endif
+
     return V_;
 }