targetCoeffTrim.C

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#include "targetCoeffTrim.H"
#include "geometricOneField.H"
#include "addToRunTimeSelectionTable.H"

using namespace Foam::constant;

// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //

namespace Foam
{
    defineTypeNameAndDebug(targetCoeffTrim, 0);

    addToRunTimeSelectionTable(trimModel, targetCoeffTrim, dictionary);
}


// * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //

template<class RhoFieldType>
Foam::vector Foam::targetCoeffTrim::calcCoeffs
(
    const RhoFieldType& rho,
    const vectorField& U,
    const scalarField& thetag,
    vectorField& force
) const
{
    rotor_.calculate(rho, U, thetag, force, false, false);

    const labelList& cells = rotor_.set().cells();
    const vectorField& C = rotor_.mesh().C();
    const List<point>& x = rotor_.x();

    const vector& origin = rotor_.coordSys().origin();
    const vector& rollAxis = rotor_.coordSys().R().e1();
    const vector& pitchAxis = rotor_.coordSys().R().e2();
    const vector& yawAxis = rotor_.coordSys().R().e3();

    scalar coeff1 = alpha_*sqr(rotor_.omega())*mathematical::pi;

    vector cf(Zero);
    forAll(cells, i)
    {
        label celli = cells[i];

        vector fc = force[celli];
        vector mc = fc^(C[celli] - origin);

        if (useCoeffs_)
        {
            scalar radius = x[i].x();
            scalar coeff2 = rho[celli]*coeff1*pow4(radius);

            // add to coefficient vector
            cf[0] += (fc & yawAxis)/(coeff2 + rootVSmall);
            cf[1] += (mc & pitchAxis)/(coeff2*radius + rootVSmall);
            cf[2] += (mc & rollAxis)/(coeff2*radius + rootVSmall);
        }
        else
        {
            cf[0] += fc & yawAxis;
            cf[1] += mc & pitchAxis;
            cf[2] += mc & rollAxis;
        }
    }

    reduce(cf, sumOp<vector>());

    return cf;
}


template<class RhoFieldType>
void Foam::targetCoeffTrim::correctTrim
(
    const RhoFieldType& rho,
    const vectorField& U,
    vectorField& force
) const
{
    if (rotor_.mesh().time().timeIndex() % calcFrequency_ == 0)
    {
        word calcType = "forces";
        if (useCoeffs_)
        {
            calcType = "coefficients";
        }

        Info<< type() << ":" << nl
            << "    solving for target trim " << calcType << nl;

        const scalar rhoRef = rotor_.rhoRef();

        // iterate to find new pitch angles to achieve target force
        scalar err = great;
        label iter = 0;
        tensor J(Zero);

        vector old = Zero;
        while ((err > tol_) && (iter < nIter_))
        {
            // cache initial theta vector
            vector theta0(theta_);

            // set initial values
            old = calcCoeffs(rho, U, thetag(), force);

            // construct Jacobian by perturbing the pitch angles
            // by +/-(dTheta_/2)
            for (label pitchI = 0; pitchI < 3; pitchI++)
            {
                theta_[pitchI] -= dTheta_/2.0;
                vector cf0 = calcCoeffs(rho, U, thetag(), force);

                theta_[pitchI] += dTheta_;
                vector cf1 = calcCoeffs(rho, U, thetag(), force);

                vector ddTheta = (cf1 - cf0)/dTheta_;

                J[pitchI + 0] = ddTheta[0];
                J[pitchI + 3] = ddTheta[1];
                J[pitchI + 6] = ddTheta[2];

                theta_ = theta0;
            }

            // calculate the change in pitch angle vector
            vector dt = inv(J) & (target_/rhoRef - old);

            // update pitch angles
            vector thetaNew = theta_ + relax_*dt;

            // update error
            err = mag(thetaNew - theta_);

            // update for next iteration
            theta_ = thetaNew;
            iter++;
        }

        if (iter == nIter_)
        {
            Info<< "    solution not converged in " << iter
                << " iterations, final residual = " << err
                << "(" << tol_ << ")" << endl;
        }
        else
        {
            Info<< "    final residual = " << err << "(" << tol_
                << "), iterations = " << iter << endl;
        }

        Info<< "    current and target " << calcType << nl
            << "        thrust  = " << old[0]*rhoRef << ", " << target_[0] << nl
            << "        pitch   = " << old[1]*rhoRef << ", " << target_[1] << nl
            << "        roll    = " << old[2]*rhoRef << ", " << target_[2] << nl
            << "    new pitch angles [deg]:" << nl
            << "        theta0  = " << radToDeg(theta_[0]) << nl
            << "        theta1c = " << radToDeg(theta_[1]) << nl
            << "        theta1s = " << radToDeg(theta_[2]) << nl
            << endl;
    }
}


// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

Foam::targetCoeffTrim::targetCoeffTrim
(
    const fv::rotorDiskSource& rotor,
    const dictionary& dict
)
:
    trimModel(rotor, dict, typeName),
    calcFrequency_(-1),
    useCoeffs_(true),
    target_(Zero),
    theta_(Zero),
    nIter_(50),
    tol_(1e-8),
    relax_(1.0),
    dTheta_(degToRad(0.1)),
    alpha_(1.0)
{
    read(dict);
}


// * * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * //

Foam::targetCoeffTrim::~targetCoeffTrim()
{}


// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

void Foam::targetCoeffTrim::read(const dictionary& dict)
{
    trimModel::read(dict);

    const dictionary& targetDict(coeffs_.subDict("target"));
    useCoeffs_ = targetDict.lookupOrDefault<bool>("useCoeffs", true);
    word ext = "";
    if (useCoeffs_)
    {
        ext = "Coeff";
    }

    target_[0] = targetDict.lookup<scalar>("thrust" + ext);
    target_[1] = targetDict.lookup<scalar>("pitch" + ext);
    target_[2] = targetDict.lookup<scalar>("roll" + ext);

    const dictionary& pitchAngleDict(coeffs_.subDict("pitchAngles"));
    theta_[0] = degToRad(pitchAngleDict.lookup<scalar>("theta0Ini"));
    theta_[1] = degToRad(pitchAngleDict.lookup<scalar>("theta1cIni"));
    theta_[2] = degToRad(pitchAngleDict.lookup<scalar>("theta1sIni"));

    coeffs_.lookup("calcFrequency") >> calcFrequency_;

    coeffs_.readIfPresent("nIter", nIter_);
    coeffs_.readIfPresent("tol", tol_);
    coeffs_.readIfPresent("relax", relax_);

    if (coeffs_.readIfPresent("dTheta", dTheta_))
    {
        dTheta_ = degToRad(dTheta_);
    }

    alpha_ = coeffs_.lookup<scalar>("alpha");
}


Foam::tmp<Foam::scalarField> Foam::targetCoeffTrim::thetag() const
{
    const List<vector>& x = rotor_.x();

    tmp<scalarField> ttheta(new scalarField(x.size()));
    scalarField& t = ttheta.ref();

    forAll(t, i)
    {
        scalar psi = x[i].y();
        t[i] = theta_[0] + theta_[1]*cos(psi) + theta_[2]*sin(psi);
    }

    return ttheta;
}


void Foam::targetCoeffTrim::correct
(
    const vectorField& U,
    vectorField& force
) const
{
    correctTrim(geometricOneField(), U, force);
}


void Foam::targetCoeffTrim::correct
(
    const volScalarField rho,
    const vectorField& U,
    vectorField& force
) const
{
    correctTrim(rho, U, force);
}


// ************************************************************************* //