diff --git a/src/turbulenceModels/incompressible/LES/SpalartAllmarasDDES/SpalartAllmarasDDES.C b/src/turbulenceModels/incompressible/LES/SpalartAllmarasDDES/SpalartAllmarasDDES.C
index 94bac661db..430c37dde6 100644
--- a/src/turbulenceModels/incompressible/LES/SpalartAllmarasDDES/SpalartAllmarasDDES.C
+++ b/src/turbulenceModels/incompressible/LES/SpalartAllmarasDDES/SpalartAllmarasDDES.C
@@ -75,6 +75,12 @@ tmp<volScalarField> SpalartAllmarasDDES::fd(const volScalarField& S) const
 }
 
 
+tmp<volScalarField> SpalartAllmarasDDES::S(const volTensorField& gradU) const
+{
+    return sqrt(2.0)*mag(symm(gradU));
+}
+
+
 tmp<volScalarField> SpalartAllmarasDDES::dTilda(const volScalarField& S) const
 {
     return max
diff --git a/src/turbulenceModels/incompressible/LES/SpalartAllmarasDDES/SpalartAllmarasDDES.H b/src/turbulenceModels/incompressible/LES/SpalartAllmarasDDES/SpalartAllmarasDDES.H
index cee8ebd21f..aeb936968f 100644
--- a/src/turbulenceModels/incompressible/LES/SpalartAllmarasDDES/SpalartAllmarasDDES.H
+++ b/src/turbulenceModels/incompressible/LES/SpalartAllmarasDDES/SpalartAllmarasDDES.H
@@ -81,6 +81,8 @@ protected:
         //- Length scale
         virtual tmp<volScalarField> dTilda(const volScalarField& S) const;
 
+        virtual tmp<volScalarField> S(const volTensorField& gradU) const;
+
 
 public: