functionObject::fieldAverage: Corrected the name of mean and variance of phase fields

Now rather than the average of "U.air" being named "U.airMean" it is correctly
named for the air phase "UMean.air".

src/functionObjects/field/fieldAverage/fieldAverageItem/fieldAverageItem.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2011-2018 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2019 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -27,12 +27,12 @@ License
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
 
-const Foam::word Foam::functionObjects::fieldAverageItem::EXT_MEAN
+const Foam::word Foam::functionObjects::fieldAverageItem::meanExt
 (
     "Mean"
 );
 
-const Foam::word Foam::functionObjects::fieldAverageItem::EXT_PRIME2MEAN
+const Foam::word Foam::functionObjects::fieldAverageItem::prime2MeanExt
 (
     "Prime2Mean"
 );

src/functionObjects/field/fieldAverage/fieldAverageItem/fieldAverageItem.H

@@ -78,16 +78,6 @@ class fieldAverageItem
 {
 public:
 
-    // Public data
-
-        // File and field name extensions
-
-            //- Mean average
-            static const word EXT_MEAN;
-
-            //- Prime-squared average
-            static const word EXT_PRIME2MEAN;
-
         //- Enumeration defining the averaging base type
         enum class baseType
         {
@@ -130,6 +120,17 @@ private:
 
 public:
 
+    // Static data
+
+        // File and field name extensions
+
+            //- Mean average
+            static const word meanExt;
+
+            //- Prime-squared average
+            static const word prime2MeanExt;
+
+
     // Constructors
 
         //- Construct null

src/functionObjects/field/fieldAverage/fieldAverageItem/fieldAverageItemIO.C

@@ -26,6 +26,7 @@ License
 #include "fieldAverageItem.H"
 #include "IOstreams.H"
 #include "dictionaryEntry.H"
+#include "IOobject.H"
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
@@ -54,8 +55,18 @@ Foam::functionObjects::fieldAverageItem::fieldAverageItem(Istream& is)
     window_ = entry.lookupOrDefault<scalar>("window", -1.0);
     windowName_ = entry.lookupOrDefault<word>("windowName", "");
 
-    meanFieldName_ = fieldName_ + EXT_MEAN;
+    meanFieldName_ = IOobject::groupName
-    prime2MeanFieldName_ = fieldName_ + EXT_PRIME2MEAN;
+    (
+        IOobject::member(fieldName_) + meanExt,
+        IOobject::group(fieldName_)
+    );
+
+    prime2MeanFieldName_ = IOobject::groupName
+    (
+        IOobject::member(fieldName_) + prime2MeanExt,
+        IOobject::group(fieldName_)
+    );
+
     if ((window_ > 0) && (windowName_ != ""))
     {
         meanFieldName_ = meanFieldName_ + "_" + windowName_;
@@ -87,9 +98,17 @@ Foam::Istream& Foam::functionObjects::operator>>
     faItem.window_ = entry.lookupOrDefault<scalar>("window", -1.0);
     faItem.windowName_ = entry.lookupOrDefault<word>("windowName", "");
 
-    faItem.meanFieldName_ = faItem.fieldName_ + fieldAverageItem::EXT_MEAN;
+    faItem.meanFieldName_ = IOobject::groupName
-    faItem.prime2MeanFieldName_ =
+    (
-        faItem.fieldName_ + fieldAverageItem::EXT_PRIME2MEAN;
+        IOobject::member(faItem.fieldName_) + fieldAverageItem::meanExt,
+        IOobject::group(faItem.fieldName_)
+    );
+
+    faItem.prime2MeanFieldName_ = IOobject::groupName
+    (
+        IOobject::member(faItem.fieldName_) + fieldAverageItem::prime2MeanExt,
+        IOobject::group(faItem.fieldName_)
+    );
 
     if ((faItem.window_ > 0) && (faItem.windowName_ != ""))
     {