targetCoeffTrim.C

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  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
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    Copyright (C) 2012-2016 OpenFOAM Foundation
    Copyright (C) 2020 OpenCFD Ltd.
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.
 
    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
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    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.
 
    You should have received a copy of the GNU General Public License
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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_.cells();
    const vectorField& C = rotor_.mesh().C();
    const List<point>& x = rotor_.x();
 
    const vector& origin = rotor_.coordSys().origin();
    const vector& rollAxis = rotor_.coordSys().e1();
    const vector& pitchAxis = rotor_.coordSys().e2();
    const vector& yawAxis = rotor_.coordSys().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
)
{
    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);
}
 
 
// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
void Foam::targetCoeffTrim::read(const dictionary& dict)
{
    trimModel::read(dict);
 
    const dictionary& targetDict(coeffs_.subDict("target"));
    useCoeffs_ = targetDict.getOrDefault("useCoeffs", true);
    word ext = "";
    if (useCoeffs_)
    {
        ext = "Coeff";
    }
 
    targetDict.readEntry("thrust" + ext, target_[0]);
    targetDict.readEntry("pitch" + ext, target_[1]);
    targetDict.readEntry("roll" + ext, target_[2]);
 
    const dictionary& pitchAngleDict(coeffs_.subDict("pitchAngles"));
    theta_[0] = degToRad(pitchAngleDict.get<scalar>("theta0Ini"));
    theta_[1] = degToRad(pitchAngleDict.get<scalar>("theta1cIni"));
    theta_[2] = degToRad(pitchAngleDict.get<scalar>("theta1sIni"));
 
    coeffs_.readEntry("calcFrequency", calcFrequency_);
 
    coeffs_.readIfPresent("nIter", nIter_);
    coeffs_.readIfPresent("tol", tol_);
    coeffs_.readIfPresent("relax", relax_);
 
    if (coeffs_.readIfPresent("dTheta", dTheta_))
    {
        dTheta_ = degToRad(dTheta_);
    }
 
    coeffs_.readIfPresent("alpha", alpha_);
}
 
 
Foam::tmp<Foam::scalarField> Foam::targetCoeffTrim::thetag() const
{
    const List<vector>& x = rotor_.x();
 
    auto ttheta = tmp<scalarField>::New(x.size());
    auto& 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
)
{
    correctTrim(geometricOneField(), U, force);
}
 
 
void Foam::targetCoeffTrim::correct
(
    const volScalarField rho,
    const vectorField& U,
    vectorField& force
)
{
    correctTrim(rho, U, force);
}
 
 
// ************************************************************************* //