void
NonlinearFluidMaterial :: giveDeviatoricStiffnessMatrix(FloatMatrix &answer, MatResponseMode mode, GaussPoint *gp,
TimeStep *tStep)
{
FloatArray eps;
double normeps2;
NonlinearFluidMaterialStatus *status = static_cast< NonlinearFluidMaterialStatus * >( this->giveStatus(gp) );
eps = status->giveTempDeviatoricStrainVector();
normeps2 = status->giveTempStrainNorm2();
answer.resize( eps.giveSize(), eps.giveSize() );
answer.zero();
for ( int i = 1; i <= answer.giveNumberOfRows(); i++ ) {
answer.at(i, i) = 1.;
}
if ( eps.giveSize() == 3 ) {
answer.at(3, 3) *= 0.5;
} else if ( eps.giveSize() == 4 ) {
answer.at(4, 4) *= 0.5;
} else {
answer.at(4, 4) *= 0.5;
answer.at(5, 5) *= 0.5;
answer.at(6, 6) *= 0.5;
}
if ( normeps2 != 0 ) {
FloatMatrix op;
if ( eps.giveSize() == 3 ) {
eps.at(3) *= 0.5;
} else if ( eps.giveSize() == 4 ) {
eps.at(4) *= 0.5;
} else {
eps.at(4) *= 0.5;
eps.at(5) *= 0.5;
eps.at(6) *= 0.5;
}
op.beDyadicProductOf(eps, eps);
answer.times( 2 * viscosity * ( 1 + c * pow(normeps2, alpha * 0.5) ) );
answer.add(2 * viscosity * c * alpha * pow(normeps2, alpha * 0.5 - 1), op);
} else {
answer.times(2 * viscosity);
}
}
void
NonlinearFluidMaterial :: giveDeviatoricStiffnessMatrix(FloatMatrix &answer, MatResponseMode mode, GaussPoint *gp,
TimeStep *atTime)
{
FloatArray eps;
double normeps = 0;
FloatMatrix op, t2;
NonlinearFluidMaterialStatus *status = static_cast< NonlinearFluidMaterialStatus * >( this->giveStatus(gp) );
eps = status->giveTempDeviatoricStrainVector();
eps.at(3) *= 0.5;
normeps = eps.at(1) * eps.at(1) + eps.at(2) * eps.at(2) + 2 * ( eps.at(3) * eps.at(3) );
normeps = sqrt(normeps);
op.resize(3, 3);
op.beDyadicProductOf(eps, eps);
if ( normeps != 0 ) {
op.times( 2 * viscosity * c * alpha * pow(normeps, alpha - 2) );
} else {
op.times(0);
}
t2.resize(3, 3);
t2.zero();
for ( int i = 1; i <= 3; i++ ) {
if ( normeps != 0 ) {
t2.at(i, i) = 2 * viscosity * ( 1 + c * pow(normeps, alpha) );
} else {
t2.at(i, i) = 2 * viscosity;
}
}
t2.at(3, 3) *= 0.5;
answer.resize(3, 3);
answer.zero();
answer.add(op);
answer.add(t2);
}
