On 9/30/21 6:49 AM, Мария Бронзова wrote:
So, there are two boundary integrals in the formulation and I am trying to
implement them for the case of fixed displacement boundary condition. The
first boundary integral falls to zero for such a BC, as no displacement
variation is possible in this case. So, I am implementing the second integral
from the second equation. The integral can be represented as in the BC.PNG
file. There are those factors in brackets, assigned displacement values and
variation of the pressure multiplied together:
*local_rhs*(i) += -porosity*(1.+Q[k]/R[k])
*d_boundary_values[q]
*fe_face_values[pressure].value(i,q)
*fe_face_values.JxW(q);
But the way it is written now it cannot work, as the *d_boundary_values* term
is a vector of vectors (as we have three displacement components). So, the
question is, whether there is a way to treat the displacement components
seperately in this *d_boundary_values* term? Or maybe even a smarter way to
make it work?
I think that your question is actually of mathematical nature, not one of
implementation. If I read the integral I_2 correctly in your previous email,
then what you prescribe there is
u^i_n
which I believe is not actually the displacement on the boundary (a vector)
but only the *normal component* of the velocity (a scalar). So you have two
options:
- You write a function that only returns the normal velocity (which is all
you can prescribe anyway)
- You write a function that returns the velocity at the boundary as a vector
and then in the bilinear form, you take the dot product with the normal
vector (which you can get from the fe_face_values object).
Both are reasonable, though if all you can prescribe is the normal component,
you might as well write your function in such a way that that is what it returns.
Best
W.
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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