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rigidBodyDynamics/rigidBodySolvers: Added run-time selectable solvers to integrate the rigid-body motion

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Currently supported solvers: symplectic, Newmark, CrankNicolson

The symplectic solver should only be used if iteration over the forces
and body-motion is not required.  Newmark and CrankNicolson both require
iteration to provide 2nd-order behavior.

See applications/test/rigidBodyDynamics/spring for an example of the
application of the Newmark solver.

This development is sponsored by Carnegie Wave Energy Ltd.
This commit is contained in:
Henry Weller
2016-04-12 11:33:20 +01:00
parent 1b90b1b9b3
commit 2870be400e
18 changed files with 1571 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
applications/test/rigidBodyDynamics/spring/spring
View File

@ -1,3 +1,11 @@
solver
{
type Newmark;
}
// It is necessary to iterate for the Newmark solver
nIter 2;
bodies
{
weight

47
applications/test/rigidBodyDynamics/spring/spring.C
View File

@ -29,7 +29,7 @@ Description
\*---------------------------------------------------------------------------*/
#include "rigidBodyModel.H"
#include "rigidBodyMotion.H"
#include "masslessBody.H"
#include "sphere.H"
#include "joints.H"
@ -45,18 +45,19 @@ using namespace RBD;
int main(int argc, char *argv[])
{
dictionary springDict(IFstream("spring")());
// Create the spring model from dictionary
rigidBodyModel spring(dictionary(IFstream("spring")()));
rigidBodyMotion spring(springDict);
label nIter(readLabel(springDict.lookup("nIter")));
Info<< spring << endl;
// Create the joint-space state fields
rigidBodyModelState springState(spring);
scalarField& q = springState.q();
scalarField& qDot = springState.qDot();
scalarField& qDdot = springState.qDdot();
// Create the joint-space force field
scalarField tau(spring.nDoF(), Zero);
// Create the external body force field
Field<spatialVector> fx(spring.nBodies(), Zero);
OFstream qFile("qVsTime");
@ -66,27 +67,23 @@ int main(int argc, char *argv[])
scalar deltaT = 0.002;
for (scalar t=0; t<4; t+=deltaT)
{
qDot += 0.5*deltaT*qDdot;
q += deltaT*qDot;
spring.newTime();
// Update the body-state prior to the evaluation of the restraints
spring.forwardDynamicsCorrection(springState);
// Accumulate the restraint forces
fx = Zero;
spring.applyRestraints(fx);
// Calculate the body acceleration for the given state
// and restraint forces
spring.forwardDynamics(springState, tau, fx);
// Update the velocity
qDot += 0.5*deltaT*qDdot;
for (label i=0; i<nIter; i++)
{
spring.update
(
deltaT,
deltaT,
tau,
fx
);
}
// Write the results for graph generation
// using 'gnuplot spring.gnuplot'
qFile << t << " " << q[0] << endl;
qDotFile << t << " " << qDot[0] << endl;
qFile << t << " " << spring.state().q()[0] << endl;
qDotFile << t << " " << spring.state().qDot()[0] << endl;
}
Info<< "\nEnd\n" << endl;