populationBalanceModel: phaseChange: Improvements

A number of improvements have been made to the population balance phase
change drift model.

- The model now checks the ordering of the phase pairs and changes the
sign of the drift rate accordingly.

- The phase change mass flux and weights are calculated for each
velocity group, so the drift rate and phase change mass flux should be
consistent for each velocity group.

- By default the phase change mass flux is distributed between the size
groups based on the interfacial area of each group. For backward
compatibility number weighting can be enabled with a new
"numberWeighted" option.

The model now requires the user to provide a list of phase pairs in the
usual parenthesised form, rather than using the name. For example:

    phaseChange
    {
        pairs ((gas and liquid));
    }

Patch contributed by Juho Peltola, VTT.

tutorials/multiphase/reactingTwoPhaseEulerFoam/RAS/wallBoilingPolyDisperse/constant/phaseProperties

@@ -99,7 +99,7 @@ populationBalanceCoeffs
         (
             phaseChange
             {
-                pairNames (gasAndLiquid);
+                pairs    ((gas and liquid));
             }
 
             densityChange{}

tutorials/multiphase/reactingTwoPhaseEulerFoam/RAS/wallBoilingPolyDisperse/system/fvSolution

@@ -28,7 +28,7 @@ solvers
         nCorr                   1;
         tolerance               1e-4;
         renormalizeOnRestart    true;
-        renormalize             false;
+        renormalize             true;
         solveOnFinalIterOnly    true;
     }
 
@@ -108,12 +108,13 @@ relaxationFactors
 {
     fields
     {
-        iDmdt           0.1;
+        iDmdt           0.2;
     }
 
     equations
     {
         ".*"            1;
+        "e\..*"         0.2;
     }
 }