BUG: sixDoFRigidBodyMotion. Fixing problems that only occur when

orientation != I at start.

Being more careful with when using directions relative to the absolute
axes or the direction of something relative to its initial direction.

Renaming p0, v0 to pInitial, vInitial to be clearer.

fixedOrientation constraint does not need a reference orientation, as
it is not to move at all, relative to any orientation, so the
Cartesian axes are fine.

src/postProcessing/functionObjects/forces/pointPatchFields/derived/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion.C

@@ -139,11 +139,13 @@ void Foam::sixDoFRigidBodyMotion::applyConstraints(scalar deltaT)
                 << ") exceeded." << nl
                 << exit(FatalError);
         }
-        else if (report_)
+
+        Info<< "sixDoFRigidBodyMotion constraints converged in "
+            << iteration << " iterations" << endl;
+
+        if (report_)
         {
-            Info<< "sixDoFRigidBodyMotion constraints converged in "
+            Info<< "Constraint force: " << cFA << nl
-                << iteration << " iterations"
-                << nl << "Constraint force: " << cFA << nl
                 << "Constraint moment: " << cMA
                 << endl;
         }
@@ -444,7 +446,7 @@ void Foam::sixDoFRigidBodyMotion::updateForce
 
 Foam::point Foam::sixDoFRigidBodyMotion::predictedPosition
 (
-    const point& p0,
+    const point& pInitial,
     const vector& deltaForce,
     const vector& deltaMoment,
     scalar deltaT
@@ -463,14 +465,14 @@ Foam::point Foam::sixDoFRigidBodyMotion::predictedPosition
     return
     (
         centreOfMassTemp
-      + (QTemp & initialQ_.T() & (p0 - initialCentreOfMass_))
+      + (QTemp & initialQ_.T() & (pInitial - initialCentreOfMass_))
     );
 }
 
 
 Foam::vector Foam::sixDoFRigidBodyMotion::predictedOrientation
 (
-    const vector& v0,
+    const vector& vInitial,
     const vector& deltaMoment,
     scalar deltaT
 ) const
@@ -481,7 +483,7 @@ Foam::vector Foam::sixDoFRigidBodyMotion::predictedOrientation
 
     rotate(QTemp, piTemp, deltaT);
 
-    return (QTemp & initialQ_.T() & v0);
+    return (QTemp & initialQ_.T() & vInitial);
 }
 
 

src/postProcessing/functionObjects/forces/pointPatchFields/derived/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion.H

@@ -287,27 +287,30 @@ public:
 
         //- Transform the given initial state pointField by the current
         //  motion state
-        inline tmp<pointField> currentPosition(const pointField& p0) const;
+        inline tmp<pointField> currentPosition
+        (
+            const pointField& pInitial
+        ) const;
 
         //- Transform the given initial state point by the current motion
         //  state
-        inline point currentPosition(const point& p0) const;
+        inline point currentPosition(const point& pInitial) const;
 
         //- Transform the given initial state direction by the current
         //  motion state
-        inline vector currentOrientation(const vector& dir0) const;
+        inline vector currentOrientation(const vector& vInitial) const;
 
         //- Access the orientation tensor, Q.
         //  globalVector = Q & bodyLocalVector
         //  bodyLocalVector = Q.T() & globalVector
-        inline const tensor& currentOrientation() const;
+        inline const tensor& orientation() const;
 
         //- Predict the position of the supplied initial state point
         //  after deltaT given the current motion state and the
         //  additional supplied force and moment
         point predictedPosition
         (
-            const point& p0,
+            const point& pInitial,
             const vector& deltaForce,
             const vector& deltaMoment,
             scalar deltaT
@@ -318,7 +321,7 @@ public:
         //  additional supplied moment
         vector predictedOrientation
         (
-            const vector& v0,
+            const vector& vInitial,
             const vector& deltaMoment,
             scalar deltaT
         ) const;

src/postProcessing/functionObjects/forces/pointPatchFields/derived/sixDoFRigidBodyMotion/sixDoFRigidBodyMotionConstraint/fixedAxis/fixedAxis.C

@@ -97,7 +97,7 @@ bool Foam::sixDoFRigidBodyMotionConstraints::fixedAxis::constrain
     {
         rotationAxis /= magRotationAxis;
 
-        const tensor& Q = motion.currentOrientation();
+        const tensor& Q = motion.orientation();
 
         // Transform rotationAxis to body local system
         rotationAxis = Q.T() & rotationAxis;

src/postProcessing/functionObjects/forces/pointPatchFields/derived/sixDoFRigidBodyMotion/sixDoFRigidBodyMotionConstraint/fixedOrientation/fixedOrientation.C

@@ -52,8 +52,7 @@ Foam::sixDoFRigidBodyMotionConstraints::fixedOrientation::fixedOrientation
     const dictionary& sDoFRBMCDict
 )
 :
-    sixDoFRigidBodyMotionConstraint(sDoFRBMCDict),
+    sixDoFRigidBodyMotionConstraint(sDoFRBMCDict)
-    fixedOrientation_()
 {
     read(sDoFRBMCDict);
 }
@@ -99,10 +98,6 @@ bool Foam::sixDoFRigidBodyMotionConstraints::fixedOrientation::constrain
             deltaT
         );
 
-        axis = (fixedOrientation_ & axis);
-
-        refDir = (fixedOrientation_ & refDir);
-
         // Removing any axis component from predictedDir
         predictedDir -= (axis & predictedDir)*axis;
 
@@ -177,23 +172,6 @@ bool Foam::sixDoFRigidBodyMotionConstraints::fixedOrientation::read
 {
     sixDoFRigidBodyMotionConstraint::read(sDoFRBMCDict);
 
-    fixedOrientation_ =
-        sDoFRBMCCoeffs_.lookupOrDefault<tensor>("fixedOrientation", I);
-
-    if (mag(mag(fixedOrientation_) - sqrt(3.0)) > 1e-9)
-    {
-        FatalErrorIn
-        (
-            "Foam::sixDoFRigidBodyMotionConstraints::fixedOrientation::read"
-            "("
-                "const dictionary& sDoFRBMCDict"
-            ")"
-        )
-            << "fixedOrientation " << fixedOrientation_
-            << " is not a rotation tensor."
-            << exit(FatalError);
-    }
-
     return true;
 }
 
@@ -203,8 +181,6 @@ void Foam::sixDoFRigidBodyMotionConstraints::fixedOrientation::write
     Ostream& os
 ) const
 {
-    os.writeKeyword("fixedOrientation")
-        << fixedOrientation_ << token::END_STATEMENT << nl;
 }
 
 // ************************************************************************* //

src/postProcessing/functionObjects/forces/pointPatchFields/derived/sixDoFRigidBodyMotion/sixDoFRigidBodyMotionConstraint/fixedOrientation/fixedOrientation.H

@@ -59,12 +59,6 @@ class fixedOrientation
     public sixDoFRigidBodyMotionConstraint
 {
 
-    // Private data
-
-        //- Reference orientation where there is no moment
-        tensor fixedOrientation_;
-
-
 public:
 
     //- Runtime type information

src/postProcessing/functionObjects/forces/pointPatchFields/derived/sixDoFRigidBodyMotion/sixDoFRigidBodyMotionI.H

@@ -222,34 +222,40 @@ inline Foam::vector& Foam::sixDoFRigidBodyMotion::tau()
 // * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * * //
 
 inline Foam::tmp<Foam::pointField>
-Foam::sixDoFRigidBodyMotion::currentPosition(const pointField& p0) const
+Foam::sixDoFRigidBodyMotion::currentPosition(const pointField& pInitial) const
 {
     return
-        (centreOfMass() + (Q() & initialQ_.T() & (p0 - initialCentreOfMass_)));
+    (
+        centreOfMass()
+      + (Q() & initialQ_.T() & (pInitial - initialCentreOfMass_)))
+    ;
 }
 
 
 inline Foam::point Foam::sixDoFRigidBodyMotion::currentPosition
 (
-    const point& p0
+    const point& pInitial
 ) const
 {
     return
-        (centreOfMass() + (Q() & initialQ_.T() & (p0 - initialCentreOfMass_)));
+    (
+        centreOfMass()
+      + (Q() & initialQ_.T() & (pInitial - initialCentreOfMass_))
+    );
 }
 
 
 inline Foam::vector Foam::sixDoFRigidBodyMotion::currentOrientation
 (
-    const vector& dir0
+    const vector& vInitial
 ) const
 {
-    return (Q() & initialQ_.T() & dir0);
+    return (Q() & initialQ_.T() & vInitial);
 }
 
 
 inline const Foam::tensor&
-Foam::sixDoFRigidBodyMotion::currentOrientation() const
+Foam::sixDoFRigidBodyMotion::orientation() const
 {
     return Q();
 }

src/postProcessing/functionObjects/forces/pointPatchFields/derived/sixDoFRigidBodyMotion/sixDoFRigidBodyMotionRestraint/linearAxialAngularSpring/linearAxialAngularSpring.C

@@ -86,7 +86,7 @@ Foam::sixDoFRigidBodyMotionRestraints::linearAxialAngularSpring::restrain
 
     vector oldDir = refQ_ & refDir;
 
-    vector newDir = motion.currentOrientation(refDir);
+    vector newDir = motion.orientation() & refDir;
 
     if (mag(oldDir & axis_) > 0.95 || mag(newDir & axis_) > 0.95)
     {
@@ -96,7 +96,7 @@ Foam::sixDoFRigidBodyMotionRestraints::linearAxialAngularSpring::restrain
 
         vector oldDir = refQ_ & refDir;
 
-        vector newDir = motion.currentOrientation(refDir);
+        vector newDir = motion.orientation() & refDir;
     }
 
     // Removing any axis component from oldDir and newDir and normalising

src/postProcessing/functionObjects/forces/pointPatchFields/derived/sixDoFRigidBodyMotion/sixDoFRigidBodyMotionRestraint/sphericalAngularSpring/sphericalAngularSpring.C

@@ -92,7 +92,7 @@ Foam::sixDoFRigidBodyMotionRestraints::sphericalAngularSpring::restrain
 
         refDir[(cmpt + 1) % 3] = 1;
 
-        vector newDir = motion.currentOrientation(refDir);
+        vector newDir = motion.orientation() & refDir;
 
         axis = (refQ_ & axis);
 

src/postProcessing/functionObjects/forces/pointPatchFields/derived/sixDoFRigidBodyMotion/sixDoFRigidBodyMotionRestraint/tabulatedAxialAngularSpring/tabulatedAxialAngularSpring.C

@@ -88,7 +88,7 @@ Foam::sixDoFRigidBodyMotionRestraints::tabulatedAxialAngularSpring::restrain
 
     vector oldDir = refQ_ & refDir;
 
-    vector newDir = motion.currentOrientation(refDir);
+    vector newDir = motion.orientation() & refDir;
 
     if (mag(oldDir & axis_) > 0.95 || mag(newDir & axis_) > 0.95)
     {
@@ -98,7 +98,7 @@ Foam::sixDoFRigidBodyMotionRestraints::tabulatedAxialAngularSpring::restrain
 
         vector oldDir = refQ_ & refDir;
 
-        vector newDir = motion.currentOrientation(refDir);
+        vector newDir = motion.orientation() & refDir;
     }
 
     // Removing any axis component from oldDir and newDir and normalising