Real
NSSUPGMass::computeQpResidual()
{
// From "Component SUPG contributions" section of the notes,
// the mass equation is stabilized by taum and the gradient of
// phi_i dotted with the momentum equation strong residuals.
// Note that the momentum equation strong residuals are stored
// in entries 1,2,3 of the "_strong_residuals" vector, regardless
// of what dimension we're solving in.
RealVectorValue Ru(
_strong_residuals[_qp][1], _strong_residuals[_qp][2], _strong_residuals[_qp][3]);
// Separate variable just for printing purposes...
Real result = _taum[_qp] * (Ru * _grad_test[_i][_qp]);
return result;
}
ZSparseMatrix RigidMotionAssembler::assemble(FESettingPtr setting) {
typedef FESetting::FEMeshPtr FEMeshPtr;
typedef Eigen::Triplet<Float> T;
std::vector<T> entries;
FEMeshPtr mesh = setting->get_mesh();
const size_t dim = mesh->getDim();
const size_t num_nodes = mesh->getNbrNodes();
// Translation part
for (size_t i=0; i<num_nodes; i++) {
for (size_t j=0; j<dim; j++) {
entries.push_back(T(j,i*dim+j, 1.0));
}
}
// Rotation part
size_t rot_degrees = 0;
if (dim == 2) {
rot_degrees = 1;
for (size_t i=0; i<num_nodes; i++) {
VectorF x = mesh->getNode(i);
entries.push_back(T(dim , i*dim , -x[1]));
entries.push_back(T(dim , i*dim+1, x[0]));
}
} else {
rot_degrees = 3;
for (size_t i=0; i<num_nodes; i++) {
VectorF x = mesh->getNode(i);
entries.push_back(T(dim , i*dim+1, -x[2]));
entries.push_back(T(dim , i*dim+2, x[1]));
entries.push_back(T(dim+1, i*dim , x[2]));
entries.push_back(T(dim+1, i*dim+2, -x[0]));
entries.push_back(T(dim+2, i*dim , -x[1]));
entries.push_back(T(dim+2, i*dim+1, x[0]));
}
}
ZSparseMatrix Ru(dim + rot_degrees, dim * num_nodes);
Ru.setFromTriplets(entries.begin(), entries.end());
return Ru;
}
