Help on understanding DeepFallingDrop2d case.

[Dip]

Can anyone help me understand, how this part works? I understand basic things, but not this part. Like why the one,two, three and four. And how can I define material properties and how can I introduce new material(solid) into the simulation?

void prepareFallingDrop(UnitConverter<T,DESCRIPTOR> const& converter,
SuperLattice<T, DESCRIPTOR>& sLattice,
SuperGeometry<T,2>& superGeometry, T lattice_size, const FreeSurfaceAppHelper& helper)
{
AnalyticalConst2D<T,T> zero( 0. );
AnalyticalConst2D<T,T> one( 1. );
AnalyticalConst2D<T,T> two( 2. );
AnalyticalConst2D<T,T> four( 4. );
FreeSurfaceDeepFallingDrop2D<T,DESCRIPTOR> cells_analytical{ lattice_size, {0., 1., 2.}};
FreeSurfaceDeepFallingDrop2D<T,DESCRIPTOR> mass_analytical{ lattice_size, {0., 0.5, 1.}};

AnalyticalConst2D<T,T> force_zero{0., 0.};

for (int i: {0,1,2}) {
sLattice.defineField<FreeSurface::MASS>(superGeometry, i, zero);
sLattice.defineField<FreeSurface::EPSILON>(superGeometry, i, zero);
sLattice.defineField<FreeSurface::CELL_TYPE>(superGeometry, i, zero);
sLattice.defineField<FreeSurface::CELL_FLAGS>(superGeometry, i, zero);
sLattice.defineField<descriptors::FORCE>(superGeometry, i, force_zero);
}

sLattice.defineField<FreeSurface::CELL_TYPE>(superGeometry, 1, cells_analytical);

sLattice.defineField<FreeSurface::MASS>(superGeometry, 1, mass_analytical);
sLattice.defineField<FreeSurface::EPSILON>(superGeometry, 1, mass_analytical);

for (int i: {0,2}) {
//sLattice.defineField<FreeSurface::MASS>(superGeometry, i, one);
sLattice.defineField<FreeSurface::EPSILON>(superGeometry, i, one);
sLattice.defineField<FreeSurface::CELL_TYPE>(superGeometry, i, four);
}

T force_factor = 1./ converter.getConversionFactorForce() * converter.getConversionFactorMass();
AnalyticalConst2D<T,T> force_a{helper.gravity_force[0] * force_factor, helper.gravity_force[1] * force_factor};
sLattice.defineField<descriptors::FORCE>(superGeometry.getMaterialIndicator(1), force_a);

}

void setInitialValues(SuperLattice<T, DESCRIPTOR>& sLattice, SuperGeometry<T,2>& sGeometry, T lattice_length, UnitConverter<T,DESCRIPTOR> const& converter, const FreeSurfaceAppHelper& helper){
OstreamManager clout( std::cout,”setInitialValues” );

std::array<T,DESCRIPTOR::d> lattice_speed;
for(size_t i = 0; i < DESCRIPTOR::d; ++i){
lattice_speed[i] = helper.initial_falling_speed[i] * converter.getPhysDeltaT() / converter.getPhysDeltaX();
}

FreeSurfaceDeepFallingDropVel2D<T,DESCRIPTOR> u{lattice_length, lattice_speed};
AnalyticalConst2D<T,T> one(1.);

sLattice.defineRhoU( sGeometry.getMaterialIndicator({0,1,2}), one, u );
for (int i: {0,1,2}) {
sLattice.iniEquilibrium( sGeometry, i, one, u );
}

// Set up free surface communicator stages
FreeSurface::initialize(sLattice);
// Make the lattice ready for simulation
sLattice.initialize();
}

[Adrian]

For modeling solid walls you can simply assign some no-slip / slip boundary condition where you want the solid obstacle to be. This is also used for the outer walls preventing the fluid from moving outside the domain in e.g. the breaking dam case.

[k8vina]

Thanks

[Author]

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