173 lines
4.3 KiB
C
173 lines
4.3 KiB
C
/*---------------------------------------------------------------------------*\
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========= |
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\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
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\\ / O peration |
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\\ / A nd | Copyright (C) 1991-2010 OpenCFD Ltd.
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\\/ M anipulation |
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-------------------------------------------------------------------------------
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License
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This file is part of OpenFOAM.
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OpenFOAM is free software: you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
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Description
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\*---------------------------------------------------------------------------*/
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#include "argList.H"
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#include "IOmanip.H"
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#include "ODE.H"
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#include "ODESolver.H"
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#include "RK.H"
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using namespace Foam;
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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class testODE
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:
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public ODE
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{
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public:
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testODE()
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{}
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label nEqns() const
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{
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return 4;
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}
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void derivatives
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(
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const scalar x,
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const scalarField& y,
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scalarField& dydx
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) const
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{
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dydx[0] = -y[1];
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dydx[1] = y[0] - (1.0/x)*y[1];
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dydx[2] = y[1] - (2.0/x)*y[2];
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dydx[3] = y[2] - (3.0/x)*y[3];
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}
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void jacobian
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(
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const scalar x,
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const scalarField& y,
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scalarField& dfdx,
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scalarSquareMatrix& dfdy
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) const
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{
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dfdx[0] = 0.0;
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dfdx[1] = (1.0/sqr(x))*y[1];
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dfdx[2] = (2.0/sqr(x))*y[2];
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dfdx[3] = (3.0/sqr(x))*y[3];
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dfdy[0][0] = 0.0;
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dfdy[0][1] = -1.0;
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dfdy[0][2] = 0.0;
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dfdy[0][3] = 0.0;
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dfdy[1][0] = 1.0;
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dfdy[1][1] = -1.0/x;
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dfdy[1][2] = 0.0;
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dfdy[1][3] = 0.0;
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dfdy[2][0] = 0.0;
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dfdy[2][1] = 1.0;
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dfdy[2][2] = -2.0/x;
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dfdy[2][3] = 0.0;
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dfdy[3][0] = 0.0;
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dfdy[3][1] = 0.0;
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dfdy[3][2] = 1.0;
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dfdy[3][3] = -3.0/x;
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}
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};
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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// Main program:
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int main(int argc, char *argv[])
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{
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argList::validArgs.append("ODESolver");
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argList args(argc, argv);
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testODE ode;
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autoPtr<ODESolver> odeSolver = ODESolver::New(args[1], ode);
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scalar xStart = 1.0;
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scalarField yStart(ode.nEqns());
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yStart[0] = ::Foam::j0(xStart);
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yStart[1] = ::Foam::j1(xStart);
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yStart[2] = ::Foam::jn(2, xStart);
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yStart[3] = ::Foam::jn(3, xStart);
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scalarField dyStart(ode.nEqns());
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ode.derivatives(xStart, yStart, dyStart);
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Info<< setw(10) << "eps" << setw(12) << "hEst";
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Info<< setw(13) << "hDid" << setw(14) << "hNext" << endl;
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Info<< setprecision(6);
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for (label i=0; i<15; i++)
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{
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scalar eps = ::Foam::exp(-scalar(i + 1));
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scalar x = xStart;
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scalarField y = yStart;
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scalarField dydx = dyStart;
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scalarField yScale(ode.nEqns(), 1.0);
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scalar hEst = 0.6;
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scalar hDid, hNext;
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odeSolver->solve(ode, x, y, dydx, eps, yScale, hEst, hDid, hNext);
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Info<< scientific << setw(13) << eps;
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Info<< fixed << setw(11) << hEst;
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Info<< setw(13) << hDid << setw(13) << hNext
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<< setw(13) << y[0] << setw(13) << y[1]
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<< setw(13) << y[2] << setw(13) << y[3]
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<< endl;
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}
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scalar x = xStart;
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scalar xEnd = x + 1.0;
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scalarField y = yStart;
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scalarField yEnd(ode.nEqns());
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yEnd[0] = ::Foam::j0(xEnd);
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yEnd[1] = ::Foam::j1(xEnd);
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yEnd[2] = ::Foam::jn(2, xEnd);
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yEnd[3] = ::Foam::jn(3, xEnd);
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scalar hEst = 0.5;
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odeSolver->solve(ode, x, xEnd, y, 1e-4, hEst);
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Info<< nl << "Analytical: y(2.0) = " << yEnd << endl;
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Info << "Numerical: y(2.0) = " << y << ", hEst = " << hEst << endl;
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Info<< "\nEnd\n" << endl;
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return 0;
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}
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// ************************************************************************* //
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