waveForcing: Added optional lambdaBoundary specification

which allows lambda to set higher in the cells adjacent to the boundary which is
particularly useful when solving for waves in a domain with no mean-flow and
wave BCs to avoid numerical stability problems where the specified wave flow
reverses into the domain.  The alternative is to use symmetry rather than wave
BCs on the side patches which is stable without using lambdaBoundary but there
is modest distortion of the wave profile adjacent to the side patches which does
not propagate into the domain due to the wave forcing.

src/waves/fvModels/forcing/forcing.C

@@ -50,6 +50,14 @@ void Foam::fv::forcing::readCoeffs()
             coeffs().lookup(lambda_.name())
         );
 
+    lambdaBoundary_ =
+        dimensionedScalar
+        (
+            lambdaBoundary_.name(),
+            lambdaBoundary_.dimensions(),
+            coeffs().lookupOrDefault(lambdaBoundary_.name(), 0)
+        );
+
     const bool foundScale = coeffs().found("scale");
     const bool foundOgn = coeffs().found("origin");
     const bool foundDir = coeffs().found("direction");
@@ -157,6 +165,22 @@ Foam::tmp<Foam::volScalarField::Internal> Foam::fv::forcing::forceCoeff
         volScalarField::Internal::New(typedName("forceCoeff"), lambda_*scale)
     );
 
+    // Damp the cells adjacent to the boundary with lambdaBoundary if specified
+    if (lambdaBoundary_.value() > 0)
+    {
+        const fvBoundaryMesh& bm = mesh().boundary();
+
+        forAll(bm, patchi)
+        {
+            if (!bm[patchi].coupled())
+            {
+                UIndirectList<scalar>(tforceCoeff.ref(), bm[patchi].faceCells())
+              = lambdaBoundary_.value()
+               *Field<scalar>(scale, bm[patchi].faceCells());
+            }
+        }
+    }
+
     // Write out the force coefficient for debugging
     if (debug && mesh().time().writeTime())
     {
@@ -185,6 +209,7 @@ Foam::fv::forcing::forcing
 :
     fvModel(name, modelType, mesh, dict),
     lambda_("lambda", dimless/dimTime, NaN),
+    lambdaBoundary_("lambdaBoundary", dimless/dimTime, 0),
     scale_(nullptr),
     origins_(),
     directions_()

src/waves/fvModels/forcing/forcing.H

@@ -65,6 +65,9 @@ protected:
         //- Damping coefficient [1/s]
         dimensionedScalar lambda_;
 
+        //- Optional boundary damping coefficient [1/s]
+        dimensionedScalar lambdaBoundary_;
+
         //- The scaling function
         autoPtr<Function1<scalar>> scale_;
 

src/waves/fvModels/waveForcing/waveForcing.H

@@ -63,6 +63,10 @@ Usage
         }
 
         lambda          0.5; // Forcing coefficient
+
+     // lambda          2;   // Optional boundary forcing coefficient
+                             // Useful when wave BCs are specified
+                             // without mean flow
     }
     \endverbatim
 

tutorials/incompressibleVoF/floatingObjectWaves/constant/fvModels

@@ -45,7 +45,8 @@ forcing
         duration    0.5;
     }
 
-    lambda      25;
+    lambda          5;
+    lambdaBoundary  25;
 }
 
 

tutorials/incompressibleVoF/floatingObjectWaves/system/controlDict

@@ -65,7 +65,7 @@ functions0
 DebugSwitches
 {
     // Write the forcing and damping scale and force fields
-    // forcing   1;
+    forcing   1;
 }
 
 // ************************************************************************* //