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1f51c8a89d
applications/test/rigidBodyDynamics/spring: Test of the linear spring with damper restraint
Damped simple harmonic motion of a weight on a spring is simulated and
the results compared with analytical solution
Test-spring
gnuplot spring.gnuplot
evince spring.eps
This development is sponsored by Carnegie Wave Energy Ltd.
110 lines
3.1 KiB
C
110 lines
3.1 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) 2016 OpenFOAM Foundation
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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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Application
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spring
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Description
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Simple weight and damped-spirng simulation with 1-DoF.
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\*---------------------------------------------------------------------------*/
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#include "rigidBodyModel.H"
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#include "masslessBody.H"
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#include "sphere.H"
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#include "joints.H"
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#include "IFstream.H"
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#include "OFstream.H"
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using namespace Foam;
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using namespace RBD;
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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int main(int argc, char *argv[])
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{
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// Create the spring model from dictionary
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rigidBodyModel spring(dictionary(IFstream("spring")()));
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Info<< spring << endl;
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// Create the joint-space state fields
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scalarField q(spring.nDoF(), Zero);
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scalarField w(spring.nw(), Zero);
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scalarField qDot(spring.nDoF(), Zero);
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scalarField qDdot(spring.nDoF(), Zero);
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scalarField tau(spring.nDoF(), Zero);
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Field<spatialVector> fx(spring.nBodies(), Zero);
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OFstream qFile("qVsTime");
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OFstream qDotFile("qDotVsTime");
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// Integrate the motion of the spring for 4s using a symplectic method
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scalar deltaT = 0.002;
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for (scalar t=0; t<4; t+=deltaT)
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{
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qDot += 0.5*deltaT*qDdot;
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q += deltaT*qDot;
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// Update the body-state prior to the evaluation of the restraints
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spring.forwardDynamicsCorrection
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(
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q,
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w,
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qDot,
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qDdot
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);
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// Accumulate the restraint forces
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fx = Zero;
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spring.applyRestraints(fx);
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// Calculate the body acceleration for the given state
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// and restraint forces
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spring.forwardDynamics
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(
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q,
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w,
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qDot,
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tau,
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fx,
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qDdot
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);
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// Update the velocity
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qDot += 0.5*deltaT*qDdot;
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// Write the results for graph generation
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// using 'gnuplot spring.gnuplot'
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qFile << t << " " << q[0] << endl;
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qDotFile << t << " " << qDot[0] << endl;
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}
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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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