[aspect-devel] Prescribed velocity BCs

[FELIPE ORELLANA ROVIROSA]

 Hey,

 Happy Holidays.

  I am trying to set up prescribed boundary conditions for velocity
vectors, on the boundaries of a 3D convecting system. I can do one single
boundary as being prescribed, but not more than one.

  I have read several threads relating to this, and it seems the prescribed
velocity modeling is based on IF statements for the coordinates. Still, I
cannot find any precise example (that can save me days of trials and
errors).

  Do I need to write all the boundary conditions in one single function?

   if (x_i coordinate > cc , Vi_0 (xj,xk) ); Vj; Vk ...

   if (x_j coordinate < hh, Vj_1);Vi, Vk

   ....

  how to encompass all the boundaries?, specifying all the 3 velocity
components (which might be functions) on each one of them..
   isn't it possible to separate the boundaries by left, right, top, .. and
write BC vector equations for each one of them?

I try and try different ways to write these instructions (subsection
Boundary velocity model), but I get parsing errors all the time, cause the
number of combinations is just enormous..

or do I need to use a plugging that makes this more feasible?

I would appreciate some guidance.
cheers,

Felipe
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