ENH: simplify assign zero for Dimensioned and Geometric fields (#3402)

- regular or forced assignment from `zero` does not need dimension
  checking:

    Old:  U = dimensionedVector(U.dimensions(), Zero);
    New:  U = Zero;

  this eliminates a fair bit of clutter and simplifies new coding
  without losing general dimension checking capabilities.

applications/solvers/basic/potentialFoam/createFields.H

@@ -15,11 +15,10 @@ volVectorField U
 // Initialise the velocity internal field to zero
 // Note: explicitly bypass evaluation of contraint patch overrides
 //       (e.g. swirlFanVelocity might lookup phi,rho)
-//U = dimensionedVector(U.dimensions(), Zero);
+//U = Zero;
 {
-    const dimensionedVector dt(U.dimensions(), Zero);
-    U.internalFieldRef() = dt;
-    U.boundaryFieldRef() = dt.value();
+    U.internalFieldRef() = Zero;
+    U.boundaryFieldRef() = Zero;
 }
 
 surfaceScalarField phi

applications/solvers/multiphase/compressibleMultiphaseInterFoam/multiphaseMixtureThermo/multiphaseMixtureThermo.C

@@ -1086,7 +1086,7 @@ void Foam::multiphaseMixtureThermo::solveAlphas
 
     MULES::limitSum(alphaPhiCorrs);
 
-    rhoPhi_ = dimensionedScalar(dimensionSet(1, 0, -1, 0, 0), Zero);
+    rhoPhi_ = Zero;
 
     volScalarField sumAlpha
     (

applications/solvers/multiphase/icoReactingMultiphaseInterFoam/laserDTRM/laserDTRM.C

@@ -557,7 +557,7 @@ void Foam::radiation::laserDTRM::calculate()
 
 
     // Reset the field
-    Q_ == dimensionedScalar(Q_.dimensions(), Zero);
+    Q_ == Zero;
 
     a_ = absorptionEmission_->a();
     e_ = absorptionEmission_->e();

applications/solvers/multiphase/multiphaseEulerFoam/pEqn.H

@@ -232,7 +232,7 @@
             surfaceScalarField mSfGradp("mSfGradp", pEqnIncomp.flux()/rAUf);
 
             phasei = 0;
-            phi = dimensionedScalar("phi", phi.dimensions(), Zero);
+            phi = Zero;
 
             for (phaseModel& phase : fluid.phases())
             {
@@ -261,7 +261,7 @@
 
             mSfGradp = pEqnIncomp.flux()/rAUf;
 
-            U = dimensionedVector("U", dimVelocity, Zero);
+            U = Zero;
 
             phasei = 0;
             for (phaseModel& phase : fluid.phases())

applications/solvers/multiphase/multiphaseInterFoam/multiphaseMixture/multiphaseMixture.C

@@ -626,7 +626,7 @@ void Foam::multiphaseMixture::solveAlphas
 
     MULES::limitSum(alphaPhiCorrs);
 
-    rhoPhi_ = dimensionedScalar(dimMass/dimTime, Zero);
+    rhoPhi_ = Zero;
 
     volScalarField sumAlpha
     (

applications/solvers/stressAnalysis/solidEquilibriumDisplacementFoam/kineticEnergyLimiter.H

@@ -14,6 +14,6 @@ if (!(runTime.timeIndex() % 5))
     if (smi < -SMALL)
     {
         Info<< "Resetting Dcorr to 0" << endl;
-        Dcorr == dimensionedVector(Dcorr.dimensions(), Zero);
+        Dcorr == Zero;
     }
 }