SphericalTensor/Identity: Added dual form

src/OpenFOAM/primitives/SphericalTensor/Identity.H

@@ -25,7 +25,8 @@ Class
     Foam::Identity
 
 Description
-    Templated Identity tensor derived from SphericalTensor.
+    Templated identity and dual space identity tensors
+    derived from SphericalTensor.
 
 \*---------------------------------------------------------------------------*/
 
@@ -51,13 +52,29 @@ class Identity
 
 public:
 
-    // Constructors
-
     //- Construct initializing the SphericalTensor to 1
     Identity()
     :
         SphericalTensor<Cmpt>(1)
     {}
+
+    //- The identity type in the dual space
+    class dual
+    :
+        public SphericalTensor<Cmpt>
+    {
+        //- Construct initializing the SphericalTensor to 1
+        dual()
+        :
+            SphericalTensor<Cmpt>(1)
+        {}
+    };
+
+    //- Return the identity in the dual space
+    inline dual operator*()
+    {
+        return dual();
+    }
 };