ENH: reference function object - retrieve reference using Function1

Note: previous behaviour to set the reference to a cell value can be recovered
by using the new 'sample' Function1

src/functionObjects/field/reference/reference.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2020 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -68,12 +68,8 @@ Foam::functionObjects::reference::reference
 )
 :
     fieldExpression(name, runTime, dict),
-    positionIsSet_(false),
-    celli_(-1),
-    interpolationScheme_("cell"),
-    scale_(1),
     localDict_(dict),
-    position_(Zero)
+    scale_(1)
 {
     read(dict);
 
@@ -98,27 +94,6 @@ bool Foam::functionObjects::reference::read(const dictionary& dict)
             Log << "    scale: " << scale_ << nl;
         }
 
-        if (dict.readIfPresent("position", position_))
-        {
-            Log << "    sample position: " << position_ << nl;
-
-            positionIsSet_ = true;
-
-            celli_ = mesh_.findCell(position_);
-
-            label celli = returnReduce(celli_, maxOp<label>());
-
-            if (celli == -1)
-            {
-                FatalIOErrorInFunction(dict)
-                    << "Sample cell could not be found at position "
-                    << position_ << exit(FatalIOError);
-            }
-
-            interpolationScheme_ =
-                dict.getOrDefault<word>("interpolationScheme", "cell");
-        }
-
         Log << endl;
 
         return true;

src/functionObjects/field/reference/reference.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2020 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -31,7 +31,7 @@ Group
 
 Description
     Computes a field whose values are offset to a reference
-    value obtained by sampling the field at a user-specified location.
+    value obtained by from a Function1.
 
     The field values are calculated using:
 
@@ -44,7 +44,7 @@ Description
         r_c             | field values at cell
         s               | optional scale factor (default = 1)
         f_{c}(t)        | current field values at cell at this time
-        f_p             | field value at position
+        f_p             | reference value
         f_{off}         | offset field value (default = 0)
     \endvartable
 
@@ -72,11 +72,12 @@ Usage
         // Mandatory (inherited) entry (runtime modifiable)
         field       <field>;
 
+        // Reference value
+        refValue    <Function1>;
+
         // Optional entries (runtime modifiable)
-        position    (0 0 0);
         scale       1.0;
         offset      0.0;
-        interpolationScheme    cell;
 
         // Optional (inherited) entries
         ...
@@ -88,10 +89,9 @@ Usage
         Property     | Description                | Type | Req'd | Dflt
         type         | Type name: reference       | word | yes   | -
         field        | Name of the operand field  | word | yes   | -
-        position     | Position to sample         | vector | no  | \<not used\>
-        scale        | Scale value                | scalar | no  | 1.0
-        offset       | Offset value               | scalar | no  | 0.0
-        interpolationScheme  | Sampling scheme    | word   | no  | cell
+        refValue     | Function1 reference value  | Function1 | yes | -
+        offset       | Offset value               | type-value | no  | zero
+        scale        | Scale factor               | scalar | no  | 1
     \endtable
 
     The inherited entries are elaborated in:
@@ -104,6 +104,7 @@ See also
     - Foam::functionObject
     - Foam::functionObjects::fvMeshFunctionObject
     - Foam::functionObjects::fieldExpression
+    - Foam::Function1
     - ExtendedCodeGuide::functionObjects::field::reference
 
 SourceFiles
@@ -135,23 +136,11 @@ class reference
 {
     // Private Data
 
-        //- Flag to indicate that the position is set
-        bool positionIsSet_;
-
-        //- Sample cell
-        label celli_;
-
-        //- Interpolation scheme
-        word interpolationScheme_;
-
-        //- Scale factor
-        scalar scale_;
-
         //- Local copy of dictionary used for construction
         dictionary localDict_;
 
-        //- Sample location
-        point position_;
+        //- Scale factor
+        scalar scale_;
 
 
     // Private Member Functions

src/functionObjects/field/reference/referenceTemplates.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2020 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -25,7 +25,7 @@ License
 
 \*---------------------------------------------------------------------------*/
 
-#include "interpolation.H"
+#include "Function1.H"
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
@@ -40,36 +40,24 @@ bool Foam::functionObjects::reference::calcType()
     {
         const VolFieldType& vf = *vfPtr;
 
+        // non-mandatory
         dimensioned<Type> offset("offset", vf.dimensions(), Zero, localDict_);
 
-        dimensioned<Type> cellValue("value", vf.dimensions(), Zero);
+        dimensioned<Type> refValue("refValue", vf.dimensions(), Zero);
 
-        if (positionIsSet_)
-        {
-            cellValue.value() = -pTraits<Type>::one*GREAT;
-
-            // Might trigger parallel comms (e.g. volPointInterpolation, if
-            // result is not yet cached) so have all processors do it
-            autoPtr<interpolation<Type>> interpolator
-            (
-                interpolation<Type>::New(interpolationScheme_, vf)
-            );
-
-            if (celli_ != -1)
-            {
-                cellValue.value() =
-                    interpolator().interpolate(position_, celli_, -1);
-            }
+        autoPtr<Function1<Type>> valuePtr
+        (
+            Function1<Type>::New("refValue", localDict_, &mesh_)
+        );
 
-            reduce(cellValue.value(), maxOp<Type>());
+        refValue.value() = valuePtr->value(this->time().value());
 
-            Log << "    sampled value: " << cellValue.value() << endl;
-        }
+        Info<< "    Reference value: " << refValue.value() << endl;
 
         return store
         (
             resultName_,
-            scale_*(vf - cellValue + offset)
+            scale_*(vf - refValue + offset)
         );
     }