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[Patrick Riesen <priesen@xxxxxxxxxxxxxxx>]

hello,

i want to zero the normal velocity on a boundary part of my 2D-domain, 
so i used something like

n = cell.n
a = ... + inner(w,dot(v,n)*n)*ds(2) + ...

in my form-file (w=testfunction, v=trialfunction).

i marked the boundary part using the "exterior facet domains" 
meshfunction, which will be picked up in assemble(..):

MeshFunction< uint >* _ext_facet_domains = 
mesh.data().create_mesh_function("exterior facet domains", 1)

*_ext_facet_domains = 5;
boundary.mark(*_ext_facet_domains, 2)

can i do this? or what is wrong with the above way? because i don't get 
zero velocities...

thank your for help,

patrick