functionObjects/fvTools/calcFvcGrad: Avoid clash with cached gradient field

Resolves bug-report http://www.openfoam.org/mantisbt/view.php?id=1828

src/postProcessing/functionObjects/fvTools/calcFvcGrad/calcFvcGradTemplates.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2012-2013 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2012-2015 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -26,6 +26,8 @@ License
 #include "fvMesh.H"
 #include "fvcGrad.H"
 
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
 template<class Type>
 Foam::GeometricField
 <
@@ -35,6 +37,8 @@ Foam::GeometricField
 >&
 Foam::calcFvcGrad::gradField(const word& gradName, const dimensionSet& dims)
 {
+    Info<< "gradField" << endl;
+
     typedef typename outerProduct<vector, Type>::type gradType;
     typedef GeometricField<gradType, fvPatchField, volMesh> vfGradType;
 
@@ -73,8 +77,6 @@ Foam::calcFvcGrad::gradField(const word& gradName, const dimensionSet& dims)
 }
 
 
-// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
-
 template<class Type>
 void Foam::calcFvcGrad::calcGrad
 (
@@ -98,7 +100,8 @@ void Foam::calcFvcGrad::calcGrad
 
         vfGradType& field = gradField<Type>(resultName, vf.dimensions());
 
-        field = fvc::grad(vf);
+        // De-reference the tmp to avoid a clash with the cached grad field
+        field = fvc::grad(vf)();
 
         processed = true;
     }
@@ -108,7 +111,8 @@ void Foam::calcFvcGrad::calcGrad
 
         vfGradType& field = gradField<Type>(resultName, sf.dimensions());
 
-        field = fvc::grad(sf);
+        // De-reference the tmp to avoid a clash with the cached grad field
+        field = fvc::grad(sf)();
 
         processed = true;
     }