ENH: tabulated6DoFMotion: add optional linear interpolation scheme

src/meshTools/solidBodyMotionFunctions/tabulated6DoFMotion/tabulated6DoFMotion.C

@@ -31,6 +31,7 @@ License
 #include "Tuple2.H"
 #include "IFstream.H"
 #include "interpolateSplineXY.H"
+#include "interpolateXY.H"
 #include "unitConversion.H"
 
 
@@ -51,6 +52,17 @@ namespace solidBodyMotionFunctions
 }
 
 
+const Foam::Enum
+<
+    Foam::solidBodyMotionFunctions::tabulated6DoFMotion::interpolationType
+>
+Foam::solidBodyMotionFunctions::tabulated6DoFMotion::interpolationTypeNames
+({
+    { interpolationType::SPLINE, "spline" },
+    { interpolationType::LINEAR, "linear" }
+});
+
+
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
 Foam::solidBodyMotionFunctions::tabulated6DoFMotion::tabulated6DoFMotion
@@ -90,12 +102,28 @@ Foam::solidBodyMotionFunctions::tabulated6DoFMotion::transformation() const
             << exit(FatalError);
     }
 
-    translationRotationVectors TRV = interpolateSplineXY
+    translationRotationVectors TRV;
-    (
+    switch (interpolator_)
-        t,
+    {
-        times_,
+        case interpolationType::SPLINE:
-        values_
+        {
-    );
+            TRV = interpolateSplineXY(t, times_, values_);
+            break;
+        }
+        case interpolationType::LINEAR:
+        {
+            TRV = interpolateXY(t, times_, values_);
+            break;
+        }
+        default:
+        {
+            FatalErrorInFunction
+                << "Unrecognised 'interpolationScheme' option: "
+                << interpolationTypeNames[interpolator_]
+                << exit(FatalError);
+            break;
+        }
+    }
 
     // Convert the rotational motion from deg to rad
     TRV[1] *= degToRad();
@@ -155,6 +183,14 @@ bool Foam::solidBodyMotionFunctions::tabulated6DoFMotion::read
 
     SBMFCoeffs_.readEntry("CofG", CofG_);
 
+    interpolator_ =
+        interpolationTypeNames.getOrDefault
+        (
+            "interpolationScheme",
+            SBMFCoeffs_,
+            interpolationType::SPLINE
+        );
+
     return true;
 }
 

src/meshTools/solidBodyMotionFunctions/tabulated6DoFMotion/tabulated6DoFMotion.H

@@ -61,7 +61,23 @@ class tabulated6DoFMotion
 :
     public solidBodyMotionFunction
 {
-    // Private data
+    // Private Enumerations
+
+        //- Options for the interpolation algorithm
+        enum class interpolationType : char
+        {
+            SPLINE = 0, //!< "Spline interpolation method"
+            LINEAR      //!< "Linear interpolation method"
+        };
+
+        //- Names for interpolationType
+        static const Enum<interpolationType> interpolationTypeNames;
+
+
+    // Private Data
+
+        //- Interpolation algorithm
+        interpolationType interpolator_;
 
         //- Time data file name read from dictionary
         fileName timeDataFileName_;