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Re: dirichletbc pointwise from meshfunction

 

Is it required to use pointwise eval of your subdomain.

i neither think that it's required, but i was testing all possible stuff. in fact, my code does work on some subdomains, but for others (e.g. where i have to do a coordinate transformation) i have some problem that some points are evaluated correctly but just come wrong in the 2D BC inflow condition. like as if some dofs got missed, the inflow profile looks like a parabolic "saw"...


  This is
usually better for when you want to mark something that won't be
counted as the boundary or a small number of points that are not in
the topological search (like lower dimension than a facet).  If you
are marking a mesh function then this should be all that is needed to
tell what points to call your BC functions on.  When you define the
function for applying the BC, it will still give you a point that you
can eval from your other mesh.

-- Andy

On Fri, Mar 26, 2010 at 5:33 AM, Patrick Riesen <priesen@xxxxxxxxxxxxxxx> wrote:
hello,

i'm under way of creating in-/outflow bc conditions by transferring a
discrete 1D flow profile function onto a boundary subdomain of a 2D mesh. I
marked the subdomain by a meshfunction and use an expression in which i
evaluate the bcs values by extracting them from the 1D discrete solution as

BCInFlowProfile::eval (Array<double>& values, const Array<double>& x) const
{
 [....]
 velocity1Dprofile.eval(values, x_eval);
 [....]

}
i want to use "pointwise" method for applying the bcs, so that the
velocities evaluated and specified on the vertices, but i get

dolfin/fem/DirichletBC.cpp:635: void
dolfin::DirichletBC::compute_bc_pointwise(std::map<unsigned int, double,
std::less<unsigned int>, std::allocator<std::pair<const unsigned int,
double> > >&, dolfin::BoundaryCondition::LocalData&) const: Assertion
`user_sub_domain' failed.


is using DirichletBC "pointwise" with a meshfunction and a subdomain id not
possible?

regards,
patrick


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