ENH: snappyHexMesh: additional parameter for layer truncation

applications/utilities/mesh/generation/snappyHexMesh/snappyHexMeshDict

@@ -310,6 +310,10 @@ addLayersControls
     //  make straight angle.
     featureAngle 60;
 
+    //- At non-patched sides allow mesh to slip if extrusion direction makes
+    //  angle larger than slipFeatureAngle.
+    slipFeatureAngle 30;
+
     //- Maximum number of snapping relaxation iterations. Should stop
     //  before upon reaching a correct mesh.
     nRelaxIter 5;

src/mesh/autoMesh/autoHexMesh/autoHexMeshDriver/autoLayerDriver.C

@@ -2800,7 +2800,7 @@ void Foam::autoLayerDriver::addLayers
         layerParams.nSmoothNormals(),
         layerParams.nSmoothSurfaceNormals(),
         layerParams.minMedianAxisAngleCos(),
-        layerParams.featureAngle(),
+        layerParams.slipFeatureAngle(),
 
         dispVec,
         medialRatio,

src/mesh/autoMesh/autoHexMesh/autoHexMeshDriver/layerParameters/layerParameters.C

@@ -61,6 +61,12 @@ Foam::layerParameters::layerParameters
         readScalar(dict.lookup("minThickness"))
     ),
     featureAngle_(readScalar(dict.lookup("featureAngle"))),
+    slipFeatureAngle_
+    (
+        dict.found("slipFeatureAngle")
+      ? readScalar(dict.lookup("slipFeatureAngle"))
+      : 0.5*featureAngle_
+    ),
     concaveAngle_
     (
         dict.lookupOrDefault("concaveAngle", defaultConcaveAngle)

src/mesh/autoMesh/autoHexMesh/autoHexMeshDriver/layerParameters/layerParameters.H

@@ -79,6 +79,8 @@ class layerParameters
 
         scalar featureAngle_;
 
+        scalar slipFeatureAngle_;
+
         scalar concaveAngle_;
 
         label nGrow_;
@@ -178,6 +180,13 @@ public:
                 return featureAngle_;
             }
 
+            //- At non-patched sides allow mesh to slip if extrusion
+            //  direction makes angle larger than slipFeatureAngle.
+            scalar slipFeatureAngle() const
+            {
+                return slipFeatureAngle_;
+            }
+
             scalar concaveAngle() const
             {
                 return concaveAngle_;