ENH: use topological merge as default for blockMesh (closes #1589)

- faster and fewer issues with high aspect ratio cells.

- `blockMesh -merge-geometric` for old behaviour

applications/utilities/mesh/generation/PDRblockMesh/PDRblockMesh.C

@@ -111,6 +111,9 @@ int main(int argc, char *argv[])
     #include "setRootCase.H"
     #include "createTime.H"
 
+    // Remove old files, unless disabled
+    const bool removeOldFiles = !args.found("noClean");
+
     // Instance for resulting mesh
     bool useTime = false;
     word meshInstance(runTime.constant());
@@ -159,7 +162,7 @@ int main(int argc, char *argv[])
         runTime.setTime(instant(meshInstance), 0);
     }
 
-    if (!args.found("noClean"))
+    if (removeOldFiles)
     {
         const fileName polyMeshPath
         (

applications/utilities/mesh/generation/blockMesh/blockMesh.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2016-2019 OpenCFD Ltd.
+    Copyright (C) 2016-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -46,6 +46,9 @@ Usage
       - \par -blockTopology
         Write the topology as a set of edges in OBJ format and exit.
 
+      - \par -merge-geometric
+        Use geometric instead of topological merging
+
       - \par -region \<name\>
         Specify alternative mesh region.
 
@@ -118,6 +121,13 @@ int main(int argc, char *argv[])
         "Write block edges and centres as obj files and exit"
     );
     argList::addBoolOption
+    (
+        "merge-geometric",
+        "Use geometric (point) merging instead of topological merging "
+        "(slower, fails with high-aspect cells. default for 1912 and earlier)",
+        true  // mark as an advanced option
+    );
+    argList::addBoolOption
     (
         "noClean",
         "Do not remove any existing polyMesh/ directory or files"
@@ -144,7 +154,18 @@ int main(int argc, char *argv[])
     #include "setRootCase.H"
     #include "createTime.H"
 
-    word regionName = polyMesh::defaultRegion;
+    // Remove old files, unless disabled
+    const bool removeOldFiles = !args.found("noClean");
+
+    // Topological merge, unless otherwise specified
+    blockMesh::mergeStrategy strategy(blockMesh::TOPOLOGICAL);
+
+    if (args.found("merge-geometric"))
+    {
+        strategy = blockMesh::GEOMETRIC;
+    }
+
+    word regionName(polyMesh::defaultRegion);
     word regionPath;
 
     // Check if the region is specified otherwise mesh the default region
@@ -183,7 +204,7 @@ int main(int argc, char *argv[])
     // Locate appropriate blockMeshDict
     #include "findBlockMeshDict.H"
 
-    blockMesh blocks(meshDict, regionName);
+    blockMesh blocks(meshDict, regionName, strategy);
 
     if (!blocks.valid())
     {
@@ -243,7 +264,7 @@ int main(int argc, char *argv[])
         runTime.setTime(instant(meshInstance), 0);
     }
 
-    if (!args.found("noClean"))
+    if (removeOldFiles)
     {
         const fileName polyMeshPath
         (

src/mesh/blockMesh/Make/files

@@ -34,8 +34,8 @@ blockMesh/blockMesh.C
 blockMesh/blockMeshCreate.C
 blockMesh/blockMeshTopology.C
 blockMesh/blockMeshCheck.C
-blockMesh/blockMeshMerge.C
-blockMesh/blockMeshMergeFast.C
+blockMesh/blockMeshMergeGeometrical.C
+blockMesh/blockMeshMergeTopological.C
 
 blockMeshTools/blockMeshTools.C
 

src/mesh/blockMesh/blockMesh/blockMesh.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2018 OpenCFD Ltd.
+    Copyright (C) 2018-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -39,13 +39,18 @@ namespace Foam
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
-Foam::blockMesh::blockMesh(const IOdictionary& dict, const word& regionName)
+Foam::blockMesh::blockMesh
+(
+    const IOdictionary& dict,
+    const word& regionName,
+    const mergeStrategy strategy
+)
 :
     meshDict_(dict),
-    verboseOutput(meshDict_.lookupOrDefault("verbose", true)),
+    verboseOutput(meshDict_.getOrDefault("verbose", true)),
     checkFaceCorrespondence_
     (
-        meshDict_.lookupOrDefault("checkFaceCorrespondence", true)
+        meshDict_.getOrDefault("checkFaceCorrespondence", true)
     ),
     geometry_
     (
@@ -63,7 +68,7 @@ Foam::blockMesh::blockMesh(const IOdictionary& dict, const word& regionName)
       : dictionary(),
         true
     ),
-    scaleFactor_(1.0),
+    scaleFactor_(1),
     blockVertices_
     (
         meshDict_.lookup("vertices"),
@@ -72,13 +77,17 @@ Foam::blockMesh::blockMesh(const IOdictionary& dict, const word& regionName)
     vertices_(Foam::vertices(blockVertices_)),
     topologyPtr_(createTopology(meshDict_, regionName))
 {
-    if (meshDict_.lookupOrDefault("fastMerge", false))
+    // TODO - extend with Enum
+
+    bool useTopoMerge = (strategy == mergeStrategy::TOPOLOGICAL);
+
+    if (meshDict_.getOrDefault("fastMerge", useTopoMerge))
     {
-        calcMergeInfoFast();
+        calcTopologicalMerge();
     }
     else
     {
-        calcMergeInfo();
+        calcGeometricalMerge();
     }
 }
 

src/mesh/blockMesh/blockMesh/blockMesh.H

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2018 OpenCFD Ltd.
+    Copyright (C) 2018-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -66,7 +66,7 @@ class blockMesh
 :
     public blockList
 {
-    // Private data
+    // Private Data
 
         //- Reference to mesh dictionary
         const IOdictionary& meshDict_;
@@ -155,11 +155,13 @@ class blockMesh
 
         void check(const polyMesh& bm, const dictionary& dict) const;
 
-        //- Determine the merge info and the final number of cells/points
-        void calcMergeInfo();
+        //- Determine merge info and final number of cells/points
+        //- based on point distances
+        void calcGeometricalMerge();
 
-        //- Determine the merge info and the final number of cells/points
-        void calcMergeInfoFast();
+        //- Determine merge info and final number of cells/points
+        //- based on block topology
+        void calcTopologicalMerge();
 
         faceList createPatchFaces(const polyPatch& patchTopologyFaces) const;
 
@@ -177,15 +179,31 @@ class blockMesh
 
 public:
 
-    // Static data members
+    // Data Types
+
+        //- The block merging strategy
+        enum mergeStrategy
+        {
+            TOPOLOGICAL,    //!< Merge using block topology
+            GEOMETRIC       //!< Merge using point geometry
+        };
+
+
+    // Static Data Members
 
         ClassName("blockMesh");
 
 
     // Constructors
 
-        //- Construct from IOdictionary
-        blockMesh(const IOdictionary& dict, const word& regionName);
+        //- Construct from IOdictionary for given region
+        //  Default is topological merging.
+        blockMesh
+        (
+            const IOdictionary& dict,
+            const word& regionName,
+            const mergeStrategy strategy = TOPOLOGICAL
+        );
 
 
     //- Destructor

src/mesh/blockMesh/blockMesh/blockMeshMergeGeometrical.C

@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
+    Copyright (C) 2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -29,7 +30,7 @@ License
 
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
-void Foam::blockMesh::calcMergeInfo()
+void Foam::blockMesh::calcGeometricalMerge()
 {
     const blockList& blocks = *this;
 

src/mesh/blockMesh/blockMesh/blockMeshMergeTopological.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2015-2016 OpenFOAM Foundation
-    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -301,7 +301,7 @@ inline label facePointN
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-void Foam::blockMesh::calcMergeInfoFast()
+void Foam::blockMesh::calcTopologicalMerge()
 {
     // Generate the static face-face map
     genFaceFaceRotMap();