ENH: kOmegaSST - added turbulence decay control terms

Based on the reference:
      Spalart, P. R. and Rumsey, C. L. (2007).
      Effective Inflow Conditions for Turbulence Models in Aerodynamic
      Calculations
      AIAA Journal, 45(10), 2544 - 2553.

The decay control default is off for backwards compatibility.  To enable
it, add the following to the coefficients dictionary

      // Optional decay control
      decayControl    yes;
      kInf            \<far-field k value\>;
      omegaInf        \<far-field omega value\>;

src/TurbulenceModels/turbulenceModels/Base/kOmegaSST/kOmegaSSTBase.C

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2015 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2016 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2016-2017 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -384,15 +384,65 @@ kOmegaSSTBase<BasicEddyViscosityModel>::kOmegaSSTBase
             IOobject::AUTO_WRITE
         ),
         this->mesh_
+    ),
+    decayControl_
+    (
+        Switch::lookupOrAddToDict
+        (
+            "decayControl",
+            this->coeffDict_,
+            false
+        )
+    ),
+    kInf_
+    (
+        dimensioned<scalar>::lookupOrAddToDict
+        (
+            "kInf",
+            this->coeffDict_,
+            k_.dimensions(),
+            0
+        )
+    ),
+    omegaInf_
+    (
+        dimensioned<scalar>::lookupOrAddToDict
+        (
+            "omegaInf",
+            this->coeffDict_,
+            omega_.dimensions(),
+            0
+        )
     )
 {
     bound(k_, this->kMin_);
     bound(omega_, this->omegaMin_);
+
+    setDecayControl(this->coeffDict_);
 }
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
+template<class BasicEddyViscosityModel>
+void kOmegaSSTBase<BasicEddyViscosityModel>::setDecayControl
+(
+    const dictionary& dict
+)
+{
+    decayControl_.readIfPresent("decayControl", this->coeffDict());
+
+    if (decayControl_)
+    {
+        kInf_.read(this->coeffDict());
+        omegaInf_.read(this->coeffDict());
+
+        Info<< "    Employing decay control with kInf:" << kInf_
+            << " and omegaInf:" << omegaInf_ << endl;
+    }
+}
+
+
 template<class BasicEddyViscosityModel>
 bool kOmegaSSTBase<BasicEddyViscosityModel>::read()
 {
@@ -412,6 +462,8 @@ bool kOmegaSSTBase<BasicEddyViscosityModel>::read()
         c1_.readIfPresent(this->coeffDict());
         F3_.readIfPresent("F3", this->coeffDict());
 
+        setDecayControl(this->coeffDict());
+
         return true;
     }
     else
@@ -476,6 +528,7 @@ void kOmegaSSTBase<BasicEddyViscosityModel>::correct()
                 alpha()*rho()*(F1() - scalar(1))*CDkOmega()/omega_(),
                 omega_
             )
+          + alpha()*rho()*beta*sqr(omegaInf_)
           + Qsas(S2(), gamma, beta)
           + omegaSource()
           + fvOptions(alpha, rho, omega_)
@@ -499,6 +552,7 @@ void kOmegaSSTBase<BasicEddyViscosityModel>::correct()
         alpha()*rho()*Pk(G)
       - fvm::SuSp((2.0/3.0)*alpha()*rho()*divU, k_)
       - fvm::Sp(alpha()*rho()*epsilonByk(F1, tgradU()), k_)
+      + alpha()*rho()*betaStar_*omegaInf_*kInf_
       + kSource()
       + fvOptions(alpha, rho, k_)
     );

src/TurbulenceModels/turbulenceModels/Base/kOmegaSST/kOmegaSSTBase.H

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2017 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -52,13 +52,21 @@ Description
     and the addition of the optional F3 term for rough walls from
     \verbatim
         Hellsten, A. (1998).
-        "Some Improvements in Menter's k-omega-SST turbulence model"
+        Some Improvements in Menter's k-omega-SST turbulence model
         29th AIAA Fluid Dynamics Conference, AIAA-98-2554.
     \endverbatim
 
+    and the optional decay control from:
+    \verbatim
+        Spalart, P. R. and Rumsey, C. L. (2007).
+        Effective Inflow Conditions for Turbulence Models in Aerodynamic
+        Calculations
+        AIAA Journal, 45(10), 2544 - 2553.
+    \endverbatim
+
     Note that this implementation is written in terms of alpha diffusion
     coefficients rather than the more traditional sigma (alpha = 1/sigma) so
-    that the blending can be applied to all coefficuients in a consistent
+    that the blending can be applied to all coefficients in a consistent
     manner.  The paper suggests that sigma is blended but this would not be
     consistent with the blending of the k-epsilon and k-omega models.
 
@@ -76,19 +84,24 @@ Description
     \verbatim
         kOmegaSSTBaseCoeffs
         {
-            alphaK1     0.85;
-            alphaK2     1.0;
-            alphaOmega1 0.5;
-            alphaOmega2 0.856;
-            beta1       0.075;
-            beta2       0.0828;
-            betaStar    0.09;
-            gamma1      5/9;
-            gamma2      0.44;
-            a1          0.31;
-            b1          1.0;
-            c1          10.0;
-            F3          no;
+            alphaK1         0.85;
+            alphaK2         1.0;
+            alphaOmega1     0.5;
+            alphaOmega2     0.856;
+            beta1           0.075;
+            beta2           0.0828;
+            betaStar        0.09;
+            gamma1          5/9;
+            gamma2          0.44;
+            a1              0.31;
+            b1              1.0;
+            c1              10.0;
+            F3              no;
+
+            // Optional decay control
+            decayControl    yes;
+            kInf            \<far-field k value\>;
+            omegaInf        \<far-field omega value\>;
         }
     \endverbatim
 
@@ -145,6 +158,7 @@ protected:
             dimensionedScalar b1_;
             dimensionedScalar c1_;
 
+            //- Flag to include the F3 term
             Switch F3_;
 
 
@@ -159,8 +173,18 @@ protected:
             volScalarField omega_;
 
 
+        // Decay control
+
+            //- Flag to include the decay control
+            Switch decayControl_;
+            dimensionedScalar omegaInf_;
+            dimensionedScalar kInf_;
+
+
     // Protected Member Functions
 
+        void setDecayControl(const dictionary& dict);
+
         virtual tmp<volScalarField> F1(const volScalarField& CDkOmega) const;
         virtual tmp<volScalarField> F2() const;
         virtual tmp<volScalarField> F3() const;