I need them just on the faces that separate the materials (fluid and
solid). The piece of code is the following, on an interface cell face I
have:
cell->face(face_number)->get_dof_indices(local_face_dof_indices_fluid,
fluid_fe_index); // select the fluid dofs sets from hp-dofs
cell->face(face_number)->get_dof_indices(local_face_dof_indices_solid,
solid_fe_index); // select the solid dofs sets from hp-dofs
// impose fluid_velocity = solid_velocity (where solid_velocity =
(solid_displacement - solid_displacement_previous_time_step) / time_step)
for (unsigned int i = 0; i < local_face_dof_indices_fluid.size(); ++i)
{
if (fe_fluid->face_system_to_component_index(i).first < dim) // select just
fluid velocity (the solution is stored as (fluid_velocity + fluid_pressure
+ solid_displacement) with (dim + 1 + dim) components)
{
auto column_index = /*todo*/ ; // need to extract the right index to select
the displacement value at the interface
constraints.add_line(local_face_dof_indices_fluid[i]);
constraints.add_entry(local_face_dof_indices_fluid[i], column_index, 1.0 /
time_step);
constraints.set_inhomogeneity(local_face_dof_indices_fluid[i], -
solution_previous_time_step(column_index) / time_step);
}
}
Basically I don't know how to extract the index (or indices) that point at
the solid displacement value on the other side of the cell face. Is there a
way to do that?
Thank you
Il giorno mercoledì 18 dicembre 2024 alle 04:27:19 UTC+1 Wolfgang Bangerth
ha scritto:
> On 12/16/24 16:12, Sclah wrote:
> >
> > I am using step-46 as starting point to implement a time dependent fsi
> problem
> > using block vectors and block matrices.
> > I successfully written the time iteration and changed everything to
> block
> > structures but I am struggling to find a method to impose the fluid
> velocity
> > equal to the displacement velocity at the interface (i.e. setting a fsi
> > kinetic coupling).
> > My approach is to use AffineConstraints::add_entry and
> > AffineConstraints::set_inhomogeneity to write something like v=(u -
> u_old) /
> > time_step, where u_old is the previous time step solution.
> > The problem is to find the right column index j required by these class
> > methods. Is there a way to find it?
>
> Where do you need them, specifically? Can you use
> cell->face(f)->get_dof_indices(...)
> for example to query the DoF indices on the face of a cell, where you're
> only
> doing this on faces that separate the two kinds of materials?
>
> Best
> W.
>
>
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