prescribedRotation.C

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    Copyright (C) 2018-2021 OpenCFD Ltd.
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License
    This file is part of OpenFOAM.
 
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    under the terms of the GNU General Public License as published by
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    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.
 
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#include "prescribedRotation.H"
#include "rigidBodyModel.H"
#include "addToRunTimeSelectionTable.H"
#include "Time.H"
 
// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
 
namespace Foam
{
namespace RBD
{
namespace restraints
{
    defineTypeNameAndDebug(prescribedRotation, 0);
 
    addToRunTimeSelectionTable
    (
        restraint,
        prescribedRotation,
        dictionary
    );
}
}
}
 
 
// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
Foam::RBD::restraints::prescribedRotation::prescribedRotation
(
    const word& name,
    const dictionary& dict,
    const rigidBodyModel& model
)
:
    restraint(name, dict, model),
    omegaSet_(nullptr),
    omega_(Zero),
    oldMom_(Zero),
    error0_(Zero),
    integral0_(Zero)
{
    read(dict);
}
 
 
// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
 
Foam::RBD::restraints::prescribedRotation::~prescribedRotation()
{}
 
 
// * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * * //
 
void Foam::RBD::restraints::prescribedRotation::restrain
(
    scalarField& tau,
    Field<spatialVector>& fx,
    const rigidBodyModelState& state
) const
{
    vector refDir = rotationTensor(vector(1, 0, 0), axis_)&vector(0, 1, 0);
 
    vector oldDir = refQ_ & refDir;
    vector newDir = model_.X0(bodyID_).E() & refDir;
 
    if (mag(oldDir & axis_) > 0.95 || mag(newDir & axis_) > 0.95)
    {
        // Directions close to the axis, changing reference
        refDir = rotationTensor(vector(1, 0, 0), axis_) & vector(0, 0, 1);
        oldDir = refQ_ & refDir;
        newDir = model_.X0(bodyID_).E() & refDir;
    }
 
    // Removing axis component from oldDir and newDir and normalising
    oldDir -= (axis_ & oldDir)*axis_;
    oldDir /= (mag(oldDir) + VSMALL);
 
    newDir -= (axis_ & newDir)*axis_;
    newDir /= (mag(newDir) + VSMALL);
 
    scalar theta = mag(acos(min(oldDir & newDir, 1.0)));
 
    // Temporary axis with sign information
    vector a = (oldDir ^ newDir);
 
    // Ensure a is in direction of axis
    a = (a & axis_)*axis_;
 
    scalar magA = mag(a);
 
    if (magA > VSMALL)
    {
        a /= magA;
    }
    else
    {
        a = Zero;
    }
 
    // Adding rotation to a given body
    vector omega = model_.v(model_.master(bodyID_)).w();
 
    scalar Inertia = mag(model_.I(model_.master(bodyID_)).Ic());
 
    // from the definition of the angular momentum:
    // moment = Inertia*ddt(omega)
 
    vector error = omegaSet_->value(model_.time().value()) - omega;
    vector integral = integral0_ + error;
    vector derivative = (error - error0_);
 
    vector moment = ((p_*error + i_*integral + d_*derivative)&a)*a;
    moment *= Inertia/model_.time().deltaTValue();
 
    moment = relax_*moment + (1- relax_)*oldMom_;
 
    if (model_.debug)
    {
        Info<< " angle  " << theta*sign(a & axis_) << endl
            << " omega  " << omega << endl
            << " wanted " << omegaSet_->value(model_.time().value()) << endl
            << " moment " << moment << endl
            << " oldDir " << oldDir << endl
            << " newDir " << newDir << endl
            << " inertia " << Inertia << endl
            << " error " << error << endl
            << " integral " << integral << endl
            << " derivative " << derivative << endl
            << " refDir " << refDir
            << endl;
    }
 
    // Accumulate the force for the restrained body
    fx[bodyIndex_] += model_.X0(bodyID_).T() & spatialVector(moment, Zero);
 
    oldMom_ = moment;
    error0_ = error;
    integral0_ = integral;
}
 
 
bool Foam::RBD::restraints::prescribedRotation::read
(
    const dictionary& dict
)
{
    restraint::read(dict);
 
    refQ_ = coeffs_.getOrDefault<tensor>("referenceOrientation", I);
 
    if (mag(mag(refQ_) - sqrt(3.0)) > ROOTSMALL)
    {
        FatalErrorInFunction
            << "referenceOrientation " << refQ_ << " is not a rotation tensor. "
            << "mag(referenceOrientation) - sqrt(3) = "
            << mag(refQ_) - sqrt(3.0) << nl
            << exit(FatalError);
    }
 
    coeffs_.readEntry("axis", axis_);
 
    const scalar magAxis(mag(axis_));
 
    coeffs_.readEntry("relax", relax_);
 
    coeffs_.readEntry("p", p_);
    coeffs_.readEntry("i", i_);
    coeffs_.readEntry("d", d_);
 
    if (magAxis > VSMALL)
    {
        axis_ /= magAxis;
    }
    else
    {
        FatalErrorInFunction
            << "axis has zero length"
            << abort(FatalError);
    }
 
    // Read the actual entry
    omegaSet_.reset(Function1<vector>::New("omega", coeffs_, &model_.time()));
 
    return true;
}
 
 
void Foam::RBD::restraints::prescribedRotation::write
(
    Ostream& os
) const
{
    restraint::write(os);
 
    os.writeEntry("referenceOrientation", refQ_);
    os.writeEntry("axis", axis_);
    omegaSet_->writeData(os);
}
 
 
// ************************************************************************* //