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

   1 /*---------------------------------------------------------------------------*\
   2   =========                 |
   3   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   4    \\    /   O peration     |
   5     \\  /    A nd           | Copyright (C) 1991-2009 OpenCFD Ltd.
   6      \\/     M anipulation  |
   7 -------------------------------------------------------------------------------
   8 License
   9     This file is part of OpenFOAM.
  10
  11     OpenFOAM is free software; you can redistribute it and/or modify it
  12     under the terms of the GNU General Public License as published by the
  13     Free Software Foundation; either version 2 of the License, or (at your
  14     option) any later version.
  15
  16     OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
  17     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  18     FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  19     for more details.
  20
  21     You should have received a copy of the GNU General Public License
  22     along with OpenFOAM; if not, write to the Free Software Foundation,
  23     Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  24
  25 \*---------------------------------------------------------------------------*/
  26
  27 #include "linearAxialAngularSpring.H"
  28 #include "addToRunTimeSelectionTable.H"
  29 #include "sixDoFRigidBodyMotion.H"
  30 #include "transform.H"
  31
  32 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
  33
  34 namespace Foam
  35 {
  36 namespace sixDoFRigidBodyMotionRestraints
  37 {
  38     defineTypeNameAndDebug(linearAxialAngularSpring, 0);
  39     addToRunTimeSelectionTable
  40     (
  41         sixDoFRigidBodyMotionRestraint,
  42         linearAxialAngularSpring,
  43         dictionary
  44     );
  45 };
  46 };
  47
  48
  49 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
  50
  51 Foam::sixDoFRigidBodyMotionRestraints::linearAxialAngularSpring::
  52 linearAxialAngularSpring
  53 (
  54     const dictionary& sDoFRBMRDict
  55 )
  56 :
  57     sixDoFRigidBodyMotionRestraint(sDoFRBMRDict),
  58     refQ_(),
  59     axis_(),
  60     stiffness_(),
  61     damping_()
  62 {
  63     read(sDoFRBMRDict);
  64 }
  65
  66
  67 // * * * * * * * * * * * * * * * * Destructors * * * * * * * * * * * * * * * //
  68
  69 Foam::sixDoFRigidBodyMotionRestraints::linearAxialAngularSpring::
  70 ~linearAxialAngularSpring()
  71 {}
  72
  73
  74 // * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * * //
  75
  76 void
  77 Foam::sixDoFRigidBodyMotionRestraints::linearAxialAngularSpring::restrain
  78 (
  79     const sixDoFRigidBodyMotion& motion,
  80     vector& restraintPosition,
  81     vector& restraintForce,
  82     vector& restraintMoment
  83 ) const
  84 {
  85     vector refDir = rotationTensor(vector(1, 0 ,0), axis_) & vector(0, 1, 0);
  86
  87     vector oldDir = refQ_ & refDir;
  88
  89     vector newDir = motion.orientation() & refDir;
  90
  91     if (mag(oldDir & axis_) > 0.95 || mag(newDir & axis_) > 0.95)
  92     {
  93         // Directions getting close to the axis, change reference
  94
  95         refDir = rotationTensor(vector(1, 0 ,0), axis_) & vector(0, 0, 1);
  96
  97         vector oldDir = refQ_ & refDir;
  98
  99         vector newDir = motion.orientation() & refDir;
 100     }
 101
 102     // Removing any axis component from oldDir and newDir and normalising
 103     oldDir -= (axis_ & oldDir)*axis_;
 104     oldDir /= (mag(oldDir) + VSMALL);
 105
 106     newDir -= (axis_ & newDir)*axis_;
 107     newDir /= (mag(newDir) + VSMALL);
 108
 109     scalar theta = mag(acos(min(oldDir & newDir, 1.0)));
 110
 111     // Temporary axis with sign information.
 112     vector a = (oldDir ^ newDir);
 113
 114     // Remove any component that is not along axis that may creep in
 115     a = (a & axis_)*axis_;
 116
 117     scalar magA = mag(a);
 118
 119     if (magA > VSMALL)
 120     {
 121         a /= magA;
 122     }
 123     else
 124     {
 125         a = vector::zero;
 126     }
 127
 128     // Damping of along axis angular velocity only
 129     restraintMoment = -stiffness_*theta*a - damping_*(motion.omega() & a)*a;
 130
 131     restraintForce = vector::zero;
 132
 133     // Not needed to be altered as restraintForce is zero, but set to
 134     // centreOfMass to be sure of no spurious moment
 135     restraintPosition = motion.centreOfMass();
 136
 137     if (motion.report())
 138     {
 139         Info<< " angle " << theta*sign(a & axis_)
 140             << " force " << restraintForce
 141             << " moment " << restraintMoment
 142             << endl;
 143     }
 144 }
 145
 146
 147 bool Foam::sixDoFRigidBodyMotionRestraints::linearAxialAngularSpring::read
 148 (
 149     const dictionary& sDoFRBMRDict
 150 )
 151 {
 152     sixDoFRigidBodyMotionRestraint::read(sDoFRBMRDict);
 153
 154     refQ_ = sDoFRBMRCoeffs_.lookupOrDefault<tensor>("referenceOrientation", I);
 155
 156     if (mag(mag(refQ_) - sqrt(3.0)) > 1e-9)
 157     {
 158         FatalErrorIn
 159         (
 160             "Foam::sixDoFRigidBodyMotionRestraints::linearAxialAngularSpring::"
 161             "read"
 162             "("
 163                 "const dictionary& sDoFRBMRDict"
 164             ")"
 165         )
 166             << "referenceOrientation " << refQ_ << " is not a rotation tensor. "
 167             << "mag(referenceOrientation) - sqrt(3) = "
 168             << mag(refQ_) - sqrt(3.0) << nl
 169             << exit(FatalError);
 170     }
 171
 172     axis_ = sDoFRBMRCoeffs_.lookup("axis");
 173
 174     scalar magAxis(mag(axis_));
 175
 176     if (magAxis > VSMALL)
 177     {
 178         axis_ /= magAxis;
 179     }
 180     else
 181     {
 182         FatalErrorIn
 183         (
 184             "Foam::sixDoFRigidBodyMotionRestraints::linearAxialAngularSpring::"
 185             "read"
 186             "("
 187                 "const dictionary& sDoFRBMCDict"
 188             ")"
 189         )
 190             << "axis has zero length"
 191             << abort(FatalError);
 192     }
 193
 194     sDoFRBMRCoeffs_.lookup("stiffness") >> stiffness_;
 195
 196     sDoFRBMRCoeffs_.lookup("damping") >> damping_;
 197
 198     return true;
 199 }
 200
 201
 202 void Foam::sixDoFRigidBodyMotionRestraints::linearAxialAngularSpring::write
 203 (
 204     Ostream& os
 205 ) const
 206 {
 207     os.writeKeyword("referenceOrientation")
 208         << refQ_ << token::END_STATEMENT << nl;
 209
 210     os.writeKeyword("axis")
 211         << axis_ << token::END_STATEMENT << nl;
 212
 213     os.writeKeyword("stiffness")
 214         << stiffness_ << token::END_STATEMENT << nl;
 215
 216     os.writeKeyword("damping")
 217         << damping_ << token::END_STATEMENT << nl;
 218 }
 219
 220 // ************************************************************************* //