chtMultiRegionFoam: Added optional hydrostatic initialisation of pressure

Class
    Foam::hydrostaticInitialisation

Description
    Optional hydrostatic initialisation of p_rgh and p by solving for and
    caching the hydrostatic ph_rgh and updating the density such that

        p = ph_rgh + rho*gh + pRef

    This initialisation process is applied at the beginning of the run (not on
    restart) if the \c hydrostaticInitialisation switch is set true in
    fvSolution/PIMPLE or fvSolution/SIMPLE.  The calculation is iterative if the
    density is a function of pressure and an optional number of iterations \c
    nHydrostaticCorrectors may be specified which defaults to 5.

applications/solvers/heatTransfer/chtMultiRegionFoam/fluid/createFluidFields.H

@@ -214,9 +214,6 @@ forAll(fluidRegions, i)
         )
     );
 
-    // Force p_rgh to be consistent with p
-    p_rghFluid[i] = thermoFluid[i].p() - rhoFluid[i]*ghFluid[i] - pRefFluid[i];
-
     fluidRegions[i].setFluxRequired(p_rghFluid[i].name());
 
     initialMassFluid[i] = fvc::domainIntegrate(rhoFluid[i]).value();

applications/solvers/heatTransfer/chtMultiRegionFoam/fluid/createFluidPressureControls.H

@@ -12,4 +12,17 @@ forAll(fluidRegions, i)
             false
         )
     );
+
+    hydrostaticInitialisation
+    (
+        p_rghFluid[i],
+        thermoFluid[i].p(),
+        rhoFluid[i],
+        UFluid[i],
+        ghFluid[i],
+        ghfFluid[i],
+        pRefFluid[i],
+        thermoFluid[i],
+        pimples.pimple(i).dict()
+    );
 }