BUG: Change the calculation of dgdt term in the pEq plus reverting compressible pEqComp until

further investigation on the consequences on dynamic mesh for compressibleInterDyMFoam.
alphaSuSp.H has to be added in the solver folder in order to make it compatible with the alpha Eq.

applications/solvers/multiphase/compressibleInterFoam/compressibleInterDyMFoam/alphaSuSp.H

@@ -0,0 +1,43 @@
+volScalarField::Internal Sp
+(
+    IOobject
+    (
+        "Sp",
+        runTime.timeName(),
+        mesh
+    ),
+    mesh,
+    dimensionedScalar("Sp", dgdt.dimensions(), 0)
+);
+
+volScalarField::Internal Su
+(
+    IOobject
+    (
+        "Su",
+        runTime.timeName(),
+        mesh
+    ),
+    mesh,
+    dimensionedScalar("Su", dgdt.dimensions(), 0)
+);
+
+forAll(dgdt, celli)
+{
+    if (dgdt[celli] > 0.0 && alpha1[celli] > 0.0)
+    {
+        Sp[celli] -= dgdt[celli]*alpha1[celli];
+        Su[celli] += dgdt[celli]*alpha1[celli];
+    }
+    else if (dgdt[celli] < 0.0 && alpha1[celli] < 1.0)
+    {
+        Sp[celli] += dgdt[celli]*(1.0 - alpha1[celli]);
+    }
+}
+
+volScalarField::Internal divU
+(
+    mesh.moving()
+  ? fvc::div(phiCN() + mesh.phi())
+  : fvc::div(phiCN())
+);

applications/solvers/multiphase/compressibleInterFoam/compressibleInterDyMFoam/pEqn.H

@@ -56,29 +56,13 @@
     }
     else
     {
-        #include "rhofs.H"
-
-        p_rghEqnComp1 =
-            pos(alpha1)
-           *(
-                (
-                    fvc::ddt(alpha1, rho1) + fvc::div(alphaPhi1*rho1f)
-                  - (fvOptions(alpha1, mixture.thermo1().rho())&rho1)
-                )/rho1
-              - fvc::ddt(alpha1) - fvc::div(alphaPhi1)
-              + (alpha1*psi1/rho1)*correction(fvm::ddt(p_rgh))
-            );
+         p_rghEqnComp1 =
+            fvc::ddt(rho1) + psi1*correction(fvm::ddt(p_rgh))
+          + fvc::div(phi, rho1) - fvc::Sp(fvc::div(phi), rho1);
 
         p_rghEqnComp2 =
-            pos(alpha2)
-           *(
-               (
-                   fvc::ddt(alpha2, rho2) + fvc::div(alphaPhi2*rho2f)
-                 - (fvOptions(alpha2, mixture.thermo2().rho())&rho2)
-               )/rho2
-             - fvc::ddt(alpha2) - fvc::div(alphaPhi2)
-             + (alpha2*psi2/rho2)*correction(fvm::ddt(p_rgh))
-            );
+            fvc::ddt(rho2) + psi2*correction(fvm::ddt(p_rgh))
+          + fvc::div(phi, rho2) - fvc::Sp(fvc::div(phi), rho2);
     }
 
     // Cache p_rgh prior to solve for density update
@@ -94,7 +78,11 @@
 
         solve
         (
-            p_rghEqnComp1() + p_rghEqnComp2() + p_rghEqnIncomp,
+            (
+                (max(alpha1, scalar(0))/rho1)*p_rghEqnComp1()
+              + (max(alpha2, scalar(0))/rho2)*p_rghEqnComp2()
+            )
+          + p_rghEqnIncomp,
             mesh.solver(p_rgh.select(pimple.finalInnerIter()))
         );
 
@@ -105,8 +93,8 @@
 
             dgdt =
             (
-                alpha1*(p_rghEqnComp2 & p_rgh)
-              - alpha2*(p_rghEqnComp1 & p_rgh)
+                pos(alpha2)*(p_rghEqnComp2 & p_rgh)/rho2
+              - pos(alpha1)*(p_rghEqnComp1 & p_rgh)/rho1
             );
 
             phi = phiHbyA + p_rghEqnIncomp.flux();
@@ -131,8 +119,11 @@
     rho = alpha1*rho1 + alpha2*rho2;
 
     // Correct p_rgh for consistency with p and the updated densities
+    p = max(p_rgh + rho*gh, pMin);
     p_rgh = p - rho*gh;
     p_rgh.correctBoundaryConditions();
 
+
+
     K = 0.5*magSqr(U);
 }