potentialFoam: Added new method to estimate the static pressure field from the velocity

Uses a form of the Euler equation in which only variation along the streamlines is considered

applications/solvers/basic/potentialFoam/potentialFoam.C

@@ -35,8 +35,8 @@ Description
 \*---------------------------------------------------------------------------*/
 
 #include "fvCFD.H"
-#include "fvIOoptionList.H"
 #include "pisoControl.H"
+#include "fvIOoptionList.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -61,6 +61,12 @@ int main(int argc, char *argv[])
         "Write the velocity potential field"
     );
 
+    argList::addBoolOption
+    (
+        "writep",
+        "Calculate and write the pressure field"
+    );
+
     #include "setRootCase.H"
     #include "createTime.H"
     #include "createMesh.H"
@@ -125,6 +131,53 @@ int main(int argc, char *argv[])
         Phi.write();
     }
 
+    // Calculate the pressure field
+    if (args.optionFound("writep"))
+    {
+        Info<< nl << "Calculating approximate pressure field" << endl;
+
+        label pRefCell = 0;
+        scalar pRefValue = 0.0;
+        setRefCell
+        (
+            p,
+            potentialFlow.dict(),
+            pRefCell,
+            pRefValue
+        );
+
+        // Calculate the flow-direction filter tensor
+        volScalarField magSqrU(magSqr(U));
+        volSymmTensorField F(sqr(U)/(magSqrU + SMALL*average(magSqrU)));
+
+        // Calculate the divergence of the flow-direction filtered div(U*U)
+        // Filtering with the flow-direction generates a more reasonable
+        // pressure distribution in regions of high velocity gradient in the
+        // direction of the flow
+        volScalarField divDivUU
+        (
+            fvc::div
+            (
+                F & fvc::div(phi, U),
+                "div(div(phi,U))"
+            )
+        );
+
+        // Solve a Poisson equation for the approximate pressure
+        while (potentialFlow.correctNonOrthogonal())
+        {
+            fvScalarMatrix pEqn
+            (
+                fvm::laplacian(p) + divDivUU
+            );
+
+            pEqn.setReference(pRefCell, pRefValue);
+            pEqn.solve();
+        }
+
+        p.write();
+    }
+
     runTime.functionObjects().end();
 
     Info<< "ExecutionTime = " << runTime.elapsedCpuTime() << " s"

tutorials/basic/potentialFoam/cylinder/Allrun

@@ -8,7 +8,7 @@ application=`getApplication`
 
 cp -r 0.org 0 > /dev/null 2>&1
 runApplication blockMesh
-runApplication $application
+runApplication $application -writePhi -writep
 runApplication streamFunction
 
 # ----------------------------------------------------------------- end-of-file

tutorials/basic/potentialFoam/cylinder/system/fvSchemes

@@ -28,6 +28,8 @@ gradSchemes
 divSchemes
 {
     default         none;
+    div(phi,U)      bounded Gauss linear;
+    div(div(phi,U)) Gauss linear;
 }
 
 laplacianSchemes

tutorials/basic/potentialFoam/cylinder/system/fvSolution

@@ -19,10 +19,20 @@ solvers
 {
     Phi
     {
-        solver          PCG;
-        preconditioner  DIC;
+        solver          GAMG;
+        smoother        DIC;
+        cacheAgglomeration on;
+        agglomerator    faceAreaPair;
+        nCellsInCoarsestLevel 10;
+        mergeLevels     1;
+
         tolerance       1e-06;
-        relTol          0;
+        relTol          0.01;
+    }
+
+    p
+    {
+        $Phi;
     }
 }
 

tutorials/basic/potentialFoam/pitzDaily/Allrun

@@ -8,7 +8,7 @@ application=`getApplication`
 
 cp -r 0.org 0 > /dev/null 2>&1
 runApplication blockMesh
-runApplication $application
+runApplication $application -writePhi -writep
 runApplication streamFunction
 
 # ----------------------------------------------------------------- end-of-file

tutorials/basic/potentialFoam/pitzDaily/system/fvSchemes

@@ -28,6 +28,8 @@ gradSchemes
 divSchemes
 {
     default         none;
+    div(phi,U)      bounded Gauss linear;
+    div(div(phi,U)) Gauss linear;
 }
 
 laplacianSchemes

tutorials/basic/potentialFoam/pitzDaily/system/fvSolution

@@ -19,17 +19,26 @@ solvers
 {
     Phi
     {
-        solver          PCG;
-        preconditioner  DIC;
+        solver          GAMG;
+        smoother        DIC;
+        cacheAgglomeration on;
+        agglomerator    faceAreaPair;
+        nCellsInCoarsestLevel 10;
+        mergeLevels     1;
+
         tolerance       1e-06;
-        relTol          0;
+        relTol          0.01;
+    }
+
+    p
+    {
+        $Phi;
     }
 }
 
 potentialFlow
 {
-    nNonOrthogonalCorrectors 0;
+    nNonOrthogonalCorrectors 2;
 }
 
-
 // ************************************************************************* //