diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/interfaceCompositionModel/interfaceCompositionModel.C b/src/phaseSystemModels/multiphaseInter/phasesSystem/interfaceCompositionModel/interfaceCompositionModel.C
index aced6c86f8..c347594f0b 100644
--- a/src/phaseSystemModels/multiphaseInter/phasesSystem/interfaceCompositionModel/interfaceCompositionModel.C
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/interfaceCompositionModel/interfaceCompositionModel.C
@@ -131,7 +131,7 @@ const Foam::word& Foam::interfaceCompositionModel::variable() const
 }
 
 
-bool Foam::interfaceCompositionModel::includeDivU()
+bool Foam::interfaceCompositionModel::includeDivU() const noexcept
 {
     return true;
 }
diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/interfaceCompositionModel/interfaceCompositionModel.H b/src/phaseSystemModels/multiphaseInter/phasesSystem/interfaceCompositionModel/interfaceCompositionModel.H
index 3993d33dc0..ae99c70404 100644
--- a/src/phaseSystemModels/multiphaseInter/phasesSystem/interfaceCompositionModel/interfaceCompositionModel.H
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/interfaceCompositionModel/interfaceCompositionModel.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -195,11 +195,11 @@ public:
         ) = 0;
 
         //- Reference value
-        virtual const dimensionedScalar& Tactivate() const = 0;
+        virtual const dimensionedScalar& Tactivate() const noexcept = 0;
 
         //- Add/subtract alpha*div(U) as a source term
         //- for alpha, substituting div(U) = mDot(1/rho1 - 1/rho2)
-        virtual bool includeDivU();
+        virtual bool includeDivU() const noexcept;
 
         //- Add volume change in pEq
         bool includeVolChange();
diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/Lee/Lee.C b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/Lee/Lee.C
index 10438bd38e..e190df0aa1 100644
--- a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/Lee/Lee.C
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/Lee/Lee.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -170,20 +170,4 @@ Foam::meltingEvaporationModels::Lee<Thermo, OtherThermo>::KSu
 }
 
 
-template<class Thermo, class OtherThermo>
-const Foam::dimensionedScalar&
-Foam::meltingEvaporationModels::Lee<Thermo, OtherThermo>::Tactivate() const
-{
-    return Tactivate_;
-}
-
-
-template<class Thermo, class OtherThermo>
-bool
-Foam::meltingEvaporationModels::Lee<Thermo, OtherThermo>::includeDivU()
-{
-    return true;
-}
-
-
 // ************************************************************************* //
diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/Lee/Lee.H b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/Lee/Lee.H
index bdaf30e6cb..7e7cc45e24 100644
--- a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/Lee/Lee.H
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/Lee/Lee.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -165,11 +165,17 @@ public:
         );
 
         //- Return T transition between phases
-        virtual const dimensionedScalar& Tactivate() const;
+        virtual const dimensionedScalar& Tactivate() const noexcept
+        {
+            return Tactivate_;
+        }
 
         //- Add/subtract alpha*div(U) as a source term
         //- for alpha, substituting div(U) = mDot(1/rho1 - 1/rho2)
-        virtual bool includeDivU();
+        virtual bool includeDivU() const noexcept
+        {
+            return true;
+        }
 };
 
 
diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/interfaceHeatResistance/interfaceHeatResistance.C b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/interfaceHeatResistance/interfaceHeatResistance.C
index 4374ac40a8..ca76c43a51 100644
--- a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/interfaceHeatResistance/interfaceHeatResistance.C
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/interfaceHeatResistance/interfaceHeatResistance.C
@@ -5,8 +5,8 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2020 OpenCFD Ltd.
     Copyright (C) 2020 Henning Scheufler
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -316,22 +316,4 @@ Foam::meltingEvaporationModels::interfaceHeatResistance<Thermo, OtherThermo>
 }
 
 
-template<class Thermo, class OtherThermo>
-const Foam::dimensionedScalar&
-Foam::meltingEvaporationModels::interfaceHeatResistance<Thermo, OtherThermo>
-::Tactivate() const
-{
-    return Tactivate_;
-}
-
-
-template<class Thermo, class OtherThermo>
-bool
-Foam::meltingEvaporationModels::
-interfaceHeatResistance<Thermo, OtherThermo>::includeDivU()
-{
-    return true;
-}
-
-
 // ************************************************************************* //
diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/interfaceHeatResistance/interfaceHeatResistance.H b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/interfaceHeatResistance/interfaceHeatResistance.H
index 9b842db2c8..7116126168 100644
--- a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/interfaceHeatResistance/interfaceHeatResistance.H
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/interfaceHeatResistance/interfaceHeatResistance.H
@@ -5,8 +5,8 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2020 OpenCFD Ltd.
     Copyright (C) 2020 Henning Scheufler
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -171,11 +171,17 @@ public:
         );
 
         //- Return Tactivate
-        virtual const dimensionedScalar& Tactivate() const;
+        virtual const dimensionedScalar& Tactivate() const noexcept
+        {
+            return Tactivate_;
+        }
 
         //- Add/subtract alpha*div(U) as a source term
         //- for alpha, substituting div(U) = mDot(1/rho1 - 1/rho2)
-        virtual bool includeDivU();
+        virtual bool includeDivU() const noexcept
+        {
+            return true;
+        }
 };
 
 
diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/kineticGasEvaporation/kineticGasEvaporation.C b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/kineticGasEvaporation/kineticGasEvaporation.C
index 3325fa786d..7b89464004 100644
--- a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/kineticGasEvaporation/kineticGasEvaporation.C
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/kineticGasEvaporation/kineticGasEvaporation.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -319,21 +319,4 @@ Foam::meltingEvaporationModels::kineticGasEvaporation<Thermo, OtherThermo>::KSu
 }
 
 
-template<class Thermo, class OtherThermo>
-const Foam::dimensionedScalar&
-Foam::meltingEvaporationModels::kineticGasEvaporation<Thermo, OtherThermo>
-::Tactivate() const
-{
-    return Tactivate_;
-}
-
-
-template<class Thermo, class OtherThermo>
-bool
-Foam::meltingEvaporationModels::
-kineticGasEvaporation<Thermo, OtherThermo>::includeDivU()
-{
-    return true;
-}
-
 // ************************************************************************* //
diff --git a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/kineticGasEvaporation/kineticGasEvaporation.H b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/kineticGasEvaporation/kineticGasEvaporation.H
index 8e4ae161b9..e9518eb65d 100644
--- a/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/kineticGasEvaporation/kineticGasEvaporation.H
+++ b/src/phaseSystemModels/multiphaseInter/phasesSystem/massTransferModels/kineticGasEvaporation/kineticGasEvaporation.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -210,11 +210,17 @@ public:
         );
 
         //- Return Tactivate
-        virtual const dimensionedScalar& Tactivate() const;
+        virtual const dimensionedScalar& Tactivate() const noexcept
+        {
+            return Tactivate_;
+        }
 
         //- Add/subtract alpha*div(U) as a source term
         //- for alpha, substituting div(U) = mDot(1/rho1 - 1/rho2)
-        virtual bool includeDivU();
+        virtual bool includeDivU() const noexcept
+        {
+            return true;
+        }
 };