ENH: user-specified ref temperature for externalCoupled mixed T BC (#1072)

- Uses the user-specified value for the HTC calculation

  {
      type  externalCoupledTemperature;

      outputTemperture    fluid;  // or wall;
      htcRefTemperature   user;   // or cell (default)

      Tref    293.15;
  }

src/functionObjects/field/externalCoupled/externalCoupledTemperatureMixed/externalCoupledTemperatureMixedFvPatchScalarField.C

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2013-2016 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2017-2018 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2017-2019 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -44,6 +44,18 @@ Foam::externalCoupledTemperatureMixedFvPatchScalarField::outputTemperatureNames
 });
 
 
+const Foam::Enum
+<
+    Foam::externalCoupledTemperatureMixedFvPatchScalarField::
+    refTemperatureType
+>
+Foam::externalCoupledTemperatureMixedFvPatchScalarField::refTemperatureNames
+({
+    { refTemperatureType::CELL, "cell" },
+    { refTemperatureType::USER, "user" },
+});
+
+
 // * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //
 
 void Foam::externalCoupledTemperatureMixedFvPatchScalarField::writeHeader
@@ -51,13 +63,13 @@ void Foam::externalCoupledTemperatureMixedFvPatchScalarField::writeHeader
     Ostream& os
 ) const
 {
-    if (outputTemperature_ == outputTemperatureType::FLUID)
+    if (outTempType_ == outputTemperatureType::WALL)
     {
-        os  << "# Values: area Tfluid qDot htc" << endl;
+        os  << "# Values: area Twall qDot htc" << endl;
     }
     else
     {
-        os  << "# Values: area Twall qDot htc" << endl;
+        os  << "# Values: area Tfluid qDot htc" << endl;
     }
 }
 
@@ -72,7 +84,9 @@ externalCoupledTemperatureMixedFvPatchScalarField
 )
 :
     externalCoupledMixedFvPatchField<scalar>(p, iF),
-    outputTemperature_(outputTemperatureType::WALL)
+    outTempType_(outputTemperatureType::WALL),
+    refTempType_(refTemperatureType::CELL),
+    Tref_(Zero)
 {}
 
 
@@ -86,7 +100,9 @@ externalCoupledTemperatureMixedFvPatchScalarField
 )
 :
     externalCoupledMixedFvPatchField<scalar>(ptf, p, iF, mapper),
-    outputTemperature_(ptf.outputTemperature_)
+    outTempType_(ptf.outTempType_),
+    refTempType_(ptf.refTempType_),
+    Tref_(ptf.Tref_)
 {}
 
 
@@ -100,12 +116,21 @@ externalCoupledTemperatureMixedFvPatchScalarField
 :
     //externalCoupledMixedFvPatchField<scalar>(p, iF, dict)
     externalCoupledMixedFvPatchField<scalar>(p, iF),
-    outputTemperature_(outputTemperatureType::WALL)
+    outTempType_(outputTemperatureType::WALL),
+    refTempType_
+    (
+        refTemperatureNames.lookupOrDefault
+        (
+            "htcRefTemperature",
+            dict,
+            refTemperatureType::CELL
+        )
+    ),
+    Tref_(Zero)
 {
     if (dict.found("outputTemperature"))
     {
-        outputTemperature_ =
-            outputTemperatureNames.get("outputTemperature", dict);
+        outTempType_ = outputTemperatureNames.get("outputTemperature", dict);
     }
     else
     {
@@ -116,6 +141,11 @@ externalCoupledTemperatureMixedFvPatchScalarField
             << endl;
     }
 
+    if (refTempType_ == refTemperatureType::USER)
+    {
+        Tref_ = dict.get<scalar>("Tref");
+    }
+
     if (dict.found("refValue"))
     {
         // Initialise same way as mixed
@@ -156,7 +186,9 @@ externalCoupledTemperatureMixedFvPatchScalarField
 )
 :
     externalCoupledMixedFvPatchField<scalar>(ecmpf),
-    outputTemperature_(ecmpf.outputTemperature_)
+    outTempType_(ecmpf.outTempType_),
+    refTempType_(ecmpf.refTempType_),
+    Tref_(ecmpf.Tref_)
 {}
 
 
@@ -168,7 +200,9 @@ externalCoupledTemperatureMixedFvPatchScalarField
 )
 :
     externalCoupledMixedFvPatchField<scalar>(ecmpf, iF),
-    outputTemperature_(ecmpf.outputTemperature_)
+    outTempType_(ecmpf.outTempType_),
+    refTempType_(ecmpf.refTempType_),
+    Tref_(ecmpf.Tref_)
 {}
 
 
@@ -224,22 +258,36 @@ void Foam::externalCoupledTemperatureMixedFvPatchScalarField::writeData
     }
 
 
-    // Patch (wall) temperature [K]
-    const scalarField& Tp(*this);
+    // Wall temperature [K]
+    const scalarField& Twall = *this;
+
+    // Fluid temperature [K]
+    tmp<scalarField> tfluid;
+
+    if (refTempType_ == refTemperatureType::USER)
+    {
+        // User-specified reference temperature
+        tfluid = tmp<scalarField>::New(size(), Tref_);
+    }
+    else
+    {
+        // Near wall cell temperature
+        tfluid = patchInternalField();
+    }
+
+    const scalarField Tfluid(tfluid);
 
-    // Near wall cell (fluid) temperature [K]
-    const scalarField Tc(patchInternalField());
 
     // Heat transfer coefficient [W/m2/K]
-    const scalarField htc(qDot/(Tp - Tc + 1e-3));
+    const scalarField htc(qDot/(Twall - Tfluid + 1e-3));
 
-    const Field<scalar>& magSf(this->patch().magSf());
+    const Field<scalar>& magSf = this->patch().magSf();
 
     const UList<scalar>& Tout =
     (
-        outputTemperature_ == outputTemperatureType::FLUID
-      ? Tc
-      : Tp
+        outTempType_ == outputTemperatureType::FLUID
+      ? Tfluid
+      : Twall
     );
 
     forAll(patch(), facei)
@@ -285,8 +333,18 @@ void Foam::externalCoupledTemperatureMixedFvPatchScalarField::write
     os.writeEntry
     (
         "outputTemperature",
-        outputTemperatureNames[outputTemperature_]
+        outputTemperatureNames[outTempType_]
     );
+    os.writeEntry
+    (
+        "htcRefTemperature",
+        refTemperatureNames[refTempType_]
+    );
+
+    if (refTempType_ == refTemperatureType::USER)
+    {
+        os.writeEntry("Tref", Tref_);
+    }
 }
 
 

src/functionObjects/field/externalCoupled/externalCoupledTemperatureMixed/externalCoupledTemperatureMixedFvPatchScalarField.H

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2013-2016 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2018 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2018-2019 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -81,7 +81,7 @@ Description
         <fileName>.in
     \endverbatim
 
-    ... and then re-instate the lock file.  The boundary condition will then
+    ... and then reinstate the lock file.  The boundary condition will then
     read the return values, and pass program execution back to OpenFOAM.
 
     To be used in combination with the functionObjects::externalCoupled
@@ -90,11 +90,11 @@ Description
 Usage
     \table
         Property | Description                              | Required | Default
-        outputTemperature | The output temperature: fluid/wall | yes |
+        outputTemperature | Output temperature: fluid/wall  | yes |
+        htcRefTemperature | Fluid temperature for htc: cell/user  | no | cell
+        Tref     | Reference temperature [K] for htc        | partly |
     \endtable
 
-Note the
-
 SeeAlso
     externalCoupledFunctionObject
     mixedFvPatchField
@@ -126,7 +126,7 @@ class externalCoupledTemperatureMixedFvPatchScalarField
 {
     // Data Types
 
-        //- Location for the ouput temperature
+        //- Location for the output temperature
         enum outputTemperatureType
         {
             FLUID,      //!< Use fluid (cell) temperature
@@ -136,11 +136,27 @@ class externalCoupledTemperatureMixedFvPatchScalarField
         //- Names for outputTemperatureType
         static const Enum<outputTemperatureType> outputTemperatureNames;
 
+        //- Reference temperature type for HTC calculation
+        enum refTemperatureType
+        {
+            CELL,       //!< Use cell temperature (default)
+            USER        //!< User-specified reference temperature
+        };
+
+        //- Names for refTemperatureType
+        static const Enum<refTemperatureType> refTemperatureNames;
+
 
     // Private Data
 
-        //- Location for the ouput temperature
-        enum outputTemperatureType outputTemperature_;
+        //- Location for the output temperature
+        enum outputTemperatureType outTempType_;
+
+        //- Reference temperature type for HTC calculation
+        enum refTemperatureType refTempType_;
+
+        //- User-specified reference temperature for HTC calculation
+        scalar Tref_;
 
 
 public: