From a430d032f544691de14e2bc1f88b2e2c76eed5dc Mon Sep 17 00:00:00 2001
From: Will Bainbridge <http://cfd.direct>
Date: Thu, 9 Feb 2023 09:46:26 +0000
Subject: [PATCH] MRF: Made compatible with non-conformal couplings (NCC)

MRF requires mapping from a given set of polyMesh cells and faces to
internal and boundary faces of the finite volume system. It therefore
has to use the polyBFacePatches and polyBFacePatchFaces maps in order to
be compatible with NCC. This has been implemented, and now MRF should be
fully compatible with NCC.
---
 .../cfdTools/general/MRF/MRFZone.C            | 152 ++++++------------
 1 file changed, 53 insertions(+), 99 deletions(-)

diff --git a/src/finiteVolume/cfdTools/general/MRF/MRFZone.C b/src/finiteVolume/cfdTools/general/MRF/MRFZone.C
index c66e52a240..1005f6fd96 100644
--- a/src/finiteVolume/cfdTools/general/MRF/MRFZone.C
+++ b/src/finiteVolume/cfdTools/general/MRF/MRFZone.C
@@ -44,48 +44,39 @@ namespace Foam
 
 void Foam::MRFZone::setMRFFaces()
 {
-    const polyBoundaryMesh& patches = mesh_.boundaryMesh();
+    const polyBoundaryMesh& pbMesh = mesh_.boundaryMesh();
+    const fvBoundaryMesh& fvbMesh = mesh_.boundary();
 
-    // Is face in MRF zone:
-    //     false: not in MRF zone
-    //     true: in MRF zone
+    // Determine cells and faces in the MRF zone
     boolList faceInMRF(mesh_.nFaces(), false);
-
-    // Determine faces in cell zone
-    // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-    // (without constructing cells)
-
-    const labelList& own = mesh_.faceOwner();
-    const labelList& nei = mesh_.faceNeighbour();
-
-    // Cells in zone
-    boolList zoneCell(mesh_.nCells(), false);
-
-    const labelUList cells = cellSet_.cells();
-    forAll(cells, i)
+    boolList cellInMRF(mesh_.nCells(), false);
     {
-        zoneCell[cells[i]] = true;
-    }
+        const labelUList MRFCells = cellSet_.cells();
 
-    for (label facei = 0; facei < mesh_.nInternalFaces(); facei++)
-    {
-        if (zoneCell[own[facei]] || zoneCell[nei[facei]])
+        forAll(MRFCells, i)
         {
-            faceInMRF[facei] = true;
+            cellInMRF[MRFCells[i]] = true;
         }
-    }
 
-    forAll(patches, patchi)
-    {
-        const polyPatch& pp = patches[patchi];
-
-        if (!isA<emptyPolyPatch>(pp))
+        for (label facei = 0; facei < mesh_.nInternalFaces(); facei++)
         {
-            forAll(pp, i)
+            if
+            (
+                cellInMRF[mesh_.faceOwner()[facei]]
+             || cellInMRF[mesh_.faceNeighbour()[facei]]
+            )
             {
-                const label facei = pp.start() + i;
+                faceInMRF[facei] = true;
+            }
+        }
 
-                if (zoneCell[own[facei]])
+        forAll(pbMesh, patchi)
+        {
+            forAll(pbMesh[patchi], patchFacei)
+            {
+                const label facei = pbMesh[patchi].start() + patchFacei;
+
+                if (cellInMRF[mesh_.faceOwner()[facei]])
                 {
                     faceInMRF[facei] = true;
                 }
@@ -96,85 +87,48 @@ void Foam::MRFZone::setMRFFaces()
     // Synchronise the faceInMRF across processor patches
     syncTools::syncFaceList(mesh_, faceInMRF, orEqOp<bool>());
 
-    // Sort into lists per patch.
+    // Construct a list of all internal FV faces in the MRF zone
+    internalFaces_ =
+        findIndices
+        (
+            SubList<bool>(faceInMRF, mesh_.nInternalFaces()),
+            true
+        );
 
-    internalFaces_.setSize(mesh_.nFaces());
-    label nInternal = 0;
-
-    for (label facei = 0; facei < mesh_.nInternalFaces(); facei++)
+    // Construct lists of patch FV faces in the MRF zone
     {
-        if (faceInMRF[facei])
+        patchFaces_.setSize(fvbMesh.size());
+
+        forAll(fvbMesh, patchi)
         {
-            internalFaces_[nInternal++] = facei;
+            patchFaces_[patchi].setSize(fvbMesh[patchi].size());
         }
-    }
-    internalFaces_.setSize(nInternal);
 
-    labelList nPatchFaces(patches.size(), 0);
+        labelList patchNFaces(fvbMesh.size(), 0);
 
-    forAll(patches, patchi)
-    {
-        const polyPatch& pp = patches[patchi];
-
-        forAll(pp, patchFacei)
+        for
+        (
+            label facei = mesh_.nInternalFaces(), bFacei = 0;
+            facei < mesh_.nFaces();
+            ++ facei, ++ bFacei
+        )
         {
-            const label facei = pp.start() + patchFacei;
+            if (!faceInMRF[facei]) continue;
 
-            if (faceInMRF[facei])
+            const labelUList patches = mesh_.polyBFacePatches()[bFacei];
+            const labelUList patchFaces = mesh_.polyBFacePatchFaces()[bFacei];
+
+            forAll(patches, i)
             {
-                nPatchFaces[patchi]++;
-            }
-        }
-    }
-
-    patchFaces_.setSize(patches.size());
-    forAll(patchFaces_, patchi)
-    {
-        patchFaces_[patchi].setSize(nPatchFaces[patchi]);
-    }
-    nPatchFaces = 0;
-
-    forAll(patches, patchi)
-    {
-        const polyPatch& pp = patches[patchi];
-
-        forAll(pp, patchFacei)
-        {
-            const label facei = pp.start() + patchFacei;
-
-            if (faceInMRF[facei])
-            {
-                patchFaces_[patchi][nPatchFaces[patchi]++] = patchFacei;
-            }
-        }
-    }
-
-
-    if (debug)
-    {
-        faceSet internalFaces(mesh_, "internalFaces", internalFaces_);
-
-        Pout<< "Writing " << internalFaces.size()
-            << " internal faces in MRF zone to faceSet "
-            << internalFaces.name() << endl;
-
-        internalFaces.write();
-
-        faceSet patchFaces(mesh_, "patchFaces", 100);
-        forAll(patchFaces_, patchi)
-        {
-            forAll(patchFaces_[patchi], i)
-            {
-                const label patchFacei = patchFaces_[patchi][i];
-                patchFaces.insert(patches[patchi].start()+patchFacei);
+                patchFaces_[patches[i]][patchNFaces[patches[i]] ++] =
+                    patchFaces[i];
             }
         }
 
-        Pout<< "Writing " << patchFaces.size()
-            << " faces in MRF zone with special handling to faceSet "
-            << patchFaces.name() << endl;
-
-        patchFaces.write();
+        forAll(fvbMesh, patchi)
+        {
+            patchFaces_[patchi].setSize(patchNFaces[patchi]);
+        }
     }
 }