TUT: use simpleGrading vs simplegrading

- add PDRblockMeshDict example for cavity

tutorials/incompressible/icoFoam/cavity/cavity/system/PDRblockMeshDict

+/*--------------------------------*- C++ -*----------------------------------*\
+| =========                 |                                                 |
+| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
+|  \\    /   O peration     | Version:  v1906                                 |
+|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
+|    \\/     M anipulation  |                                                 |
+\*---------------------------------------------------------------------------*/
+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       dictionary;
+    object      PDRblockMeshDict;
+}
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+scale   0.1;
+
+x
+{
+    points  (0 1);
+    nCells  (20);
+    ratios  (1);
+}
+
+y
+{
+    points  (0 1);
+    nCells  (20);
+    ratios  (1);
+}
+
+z
+{
+    points  (0 0.1);
+    nCells  (1);
+    ratios  (1);
+}
+
+
+boundary
+(
+    movingWall
+    {
+        type  wall;
+        faces (3);
+    }
+    fixedWalls
+    {
+        type  wall;
+        faces (0 1 2);
+    }
+    frontAndBack
+    {
+        type  empty;
+        faces (4 5);
+    }
+);
+
+
+// ************************************************************************* //

tutorials/multiphase/compressibleInterDyMFoam/laminar/sphereDrop/system/blockMeshDict

@@ -165,11 +165,11 @@ invBlockGrading #calc "1.0/$blockGrading";
 
 blocks
 (
-    hex (16 17 18 19 12 13 14 15) farField (25 100 1) simplegrading (1 1 1)
+    hex (16 17 18 19 12 13 14 15) farField (25 100 1) simpleGrading (1 1 1)
 
-    hex (3 0 1 4 2 0 1 5) bottomBlock (10 50 1) simplegrading ($edgeNumber 1 1)
+    hex (3 0 1 4 2 0 1 5) bottomBlock (10 50 1) simpleGrading ($edgeNumber 1 1)
 
-    hex (7 8 11 10 6 8 11 9) topBlock (10 35 1) simplegrading ($edgeNumber 1 1)
+    hex (7 8 11 10 6 8 11 9) topBlock (10 35 1) simpleGrading ($edgeNumber 1 1)
 
     hex (25 23 20 22 24 23 20 21)
     centralBlock (10 20 1)