ENH: reference FO - position entry is now optional

src/functionObjects/field/reference/reference.C

@@ -75,6 +75,7 @@ Foam::functionObjects::reference::reference
     fieldExpression(name, runTime, dict),
     localDict_(dict),
     position_(point::zero),
+    positionIsSet_(false),
     celli_(-1),
     interpolationScheme_("cell"),
     scale_(1)
@@ -98,24 +99,28 @@ bool Foam::functionObjects::reference::read(const dictionary& dict)
     {
         localDict_ = dict;
 
-        dict.lookup("position") >> position_;
+        if (dict.readIfPresent("position", position_))
+        {
+            positionIsSet_ = true;
 
-        interpolationScheme_ =
+            celli_ = mesh_.findCell(position_);
-            dict.lookupOrDefault<word>("interpolationScheme", "cell");
+
+            label celli = returnReduce(celli_, maxOp<label>());
+
+            if (celli == -1)
+            {
+                FatalErrorInFunction
+                    << "Sample cell could not be found at position " << position_
+                    << exit(FatalError);
+            }
+
+            interpolationScheme_ =
+                dict.lookupOrDefault<word>("interpolationScheme", "cell");
+        }
 
 
         dict.readIfPresent("scale", scale_);
 
-        celli_ = mesh_.findCell(position_);
-
-        label celli = returnReduce(celli_, maxOp<label>());
-
-        if (celli == -1)
-        {
-            FatalErrorInFunction
-                << "Sample cell could not be found at position " << position_
-                << exit(FatalError);
-        }
 
         Log << type() << " " << name() << nl
             << "    field: " << fieldName_ << nl

src/functionObjects/field/reference/reference.H

@@ -34,16 +34,16 @@ Description
     The field values are calculated using:
 
     \f[
-        f_c = s(f_{c,t} - f_p + f_{off})
+        ref_c = s(f_{c}(t) - f_p + f_{off})
     \f]
 
     where
     \vartable
-        f_c     | field values at cell
+        ref_c    | field values at cell
-        s       | optional scale factor (default = 1)
+        s        | optional scale factor (default = 1)
-        f_{c,t} | current field values at cell at this time
+        f_{c}(t) | current field values at cell at this time
-        f_p     | field value at position
+        f_p      | field value at position
-        f_{off} | offset field value (default = 0)
+        f_{off}  | offset field value (default = 0)
     \endvartable
 
 Usage
@@ -66,12 +66,11 @@ Usage
     \table
         Property     | Description             | Required | Default value
         type         | Type name: reference    | yes      |
-        position     | Position to sample      | yes      |
         field        | Name of field           | yes      |
-        reult        | Name of result field    | no       | reference(<field>)
+        result       | Name of result field    | no       | reference(<field>)
+        position     | Position to sample      | no       | <not used>
         scale        | Scale value             | no       | 1
         offset       | Offset value            | no       | zero
-        result       | Name of result field    | no       | <function name>
         log          | Log to standard output  | no       | yes
     \endtable
 
@@ -114,6 +113,9 @@ class reference
         //- Sample location
         point position_;
 
+        //- Flag to indicate that the position is set
+        bool positionIsSet_;
+
         //- Sample cell
         label celli_;
 

src/functionObjects/field/reference/referenceTemplates.C

@@ -32,22 +32,10 @@ bool Foam::functionObjects::reference::calcType()
 
     const VolFieldType* vfPtr = lookupObjectPtr<VolFieldType>(fieldName_);
 
-    if (vfPtr && celli_ != -1)
+    if (vfPtr)
     {
         const VolFieldType& vf = *vfPtr;
 
-        autoPtr<interpolation<Type>> interpolator
-        (
-            interpolation<Type>::New(interpolationScheme_, vf)
-        );
-
-        const dimensioned<Type> value
-        (
-            "value",
-            vf.dimensions(),
-            interpolator().interpolate(position_, celli_, -1)
-        );
-
         dimensioned<Type> offset
         (
             dimensioned<Type>::lookupOrDefault
@@ -59,12 +47,32 @@ bool Foam::functionObjects::reference::calcType()
             )
         );
 
-        Log << "    sampled value: " << value.value() << endl;
+        dimensioned<Type> cellValue("value", vf.dimensions(), Zero);
+
+        if (positionIsSet_)
+        {
+            cellValue.value() = -pTraits<Type>::one*GREAT;
+
+            if (celli_ != -1)
+            {
+                autoPtr<interpolation<Type>> interpolator
+                (
+                    interpolation<Type>::New(interpolationScheme_, vf)
+                );
+
+                cellValue.value() =
+                    interpolator().interpolate(position_, celli_, -1);
+            }
+
+            reduce(cellValue.value(), maxOp<Type>());
+
+            Log << "    sampled value: " << cellValue.value() << endl;
+        }
 
         return store
         (
             resultName_,
-            scale_*(vf - value + offset)
+            scale_*(vf - cellValue + offset)
         );
     }