ENH: bounding box clipping for ensightWrite function object (issue #973)

- for larger problems with a smaller region of interest, can apply a
  bounding to limit the size of the ensight geometry and fields created.

  Since the implementation uses a fvMeshSubset, there is an additional
  per-process memory overhead.

  A high output frequency should be avoided with moving meshes, since
  this indirectly forces a frequent update of the submesh.

tutorials/incompressible/simpleFoam/windAroundBuildings/Allrun-parallel

@@ -0,0 +1,16 @@
+#!/bin/sh
+cd ${0%/*} || exit 1                        # Run from this directory
+. $WM_PROJECT_DIR/bin/tools/RunFunctions    # Tutorial run functions
+
+runApplication surfaceFeatureExtract
+
+runApplication blockMesh
+runApplication snappyHexMesh -overwrite
+
+runApplication decomposePar
+
+runParallel $(getApplication)
+
+runApplication reconstructPar
+
+#------------------------------------------------------------------------------

tutorials/incompressible/simpleFoam/windAroundBuildings/system/decomposeParDict

@@ -0,0 +1,23 @@
+/*--------------------------------*- C++ -*----------------------------------*\
+| =========                 |                                                 |
+| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
+|  \\    /   O peration     | Version:  v1806                                 |
+|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
+|    \\/     M anipulation  |                                                 |
+\*---------------------------------------------------------------------------*/
+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       dictionary;
+    object      decomposeParDict;
+}
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+numberOfSubdomains 6;
+
+// method          kahip;
+method          scotch;
+
+
+// ************************************************************************* //

tutorials/incompressible/simpleFoam/windAroundBuildings/system/ensightWrite

@@ -12,6 +12,9 @@ ensightWrite
     // Fields to output (words or regex)
     fields  (U p "(k|epsilon|omega)");
 
+    // Limit output region
+    bounds  (0 0 0) (245 180 80);
+
     //- Write more frequent than fields
     writeControl    timeStep;
     writeInterval   5;