BUG: Add compressible bool for closed volume domains

applications/solvers/heatTransfer/buoyantSimpleFoam/pEqn.H

@@ -34,6 +34,7 @@
         )/(mesh.magSf().boundaryField()*rhorAUf.boundaryField())
     );
 
+
     while (simple.correctNonOrthogonal())
     {
         fvScalarMatrix p_rghEqn
@@ -64,9 +65,12 @@
 
     p = p_rgh + rho*gh;
 
+    dimensionedScalar compressibility = fvc::domainIntegrate(psi);
+    bool compressible = (compressibility.value() > SMALL);
+
     // For closed-volume cases adjust the pressure level
     // to obey overall mass continuity
-    if (closedVolume)
+    if (closedVolume && compressible)
     {
         p += (initialMass - fvc::domainIntegrate(psi*p))
             /fvc::domainIntegrate(psi);