ENH: Moving electric sources mapped from external meshes

Problem

As of the current state of OpenFOAM, the following capabilities are not available:

• The ability to dynamically update cell selections in fvOptions through input dictionary updates.
• The absence of support in fvOptions for handling moving selections, such as moving points.
• The inability to map static fields from external sources for further processing, for instance, when dealing with moving static electric-source fields within an electric field being simulated.

Solution

• The cellSetOption (hence, all fvOptions derived from the cellSetOption) received three new optional input:
  • movingPoints: Use cells containing a given set of moving points.
  • mesh: Select cells based on a given secondary mesh.
  • updateSelection: Flag to enable selection updates.
• New templated fvOption to constrain values of given fields with a source field from an external mesh: <Type>MapFieldConstraint.
• A new hook to electricPotential function object to accomodate internal fvOption constraints.

Verification

• (Heuristic) Test cases:moving-electric-potential.zip (Prior to the review changes)

Risks

• No change in existing input/output.

Metadata

• linux64ClangDPInt32Opt (clang13)
• linux64GccDPInt32Opt
• linux64GccSPDPInt64Debug
• Alltest: No new error/No change in existing output

src/functionObjects/solvers/electricPotential/electricPotential.C

@@ -217,6 +217,7 @@ Foam::functionObjects::electricPotential::electricPotential
             IOobject::scopedName(typeName, "E")
         )
     ),
+    fvOptions_(mesh_),
     nCorr_(1),
     writeDerivedFields_(false),
     electricField_(false)
@@ -341,7 +342,12 @@ bool Foam::functionObjects::electricPotential::read(const dictionary& dict)
         }
     }
 
-    return false;
+    if (const dictionary* dictptr = dict.findDict("fvOptions"))
+    {
+        fvOptions_.reset(*dictptr);
+    }
+
+    return true;
 }
 
 
@@ -359,4+365,4 @@
         fvScalarMatrix eVEqn
         (
           - fvm::laplacian(sigma, eV)
         );
 
         eVEqn.relax();
 
+        fvOptions_.constrain(eVEqn);
+
         eVEqn.solve();
     }