Boundary Condition: Antisymmetric periodicity
Has anyone come across boundary conditions in OpenFoam that impose anti-symmetric periodicity …
An anti-symmetric periodic boundary condition is just like periodic boundary conditions only swapped or mirrored … i.e. u(x, y)=u(x+L, ymax-y) v(x, y)=-v(x+L, ymax-y) p(x, y)=p(x+L, ymax-y) rather then (pure periodicity): u(x, y)=u(x+L, y) v(x, y)=v(x+L, y) p(x, y)=p(x+L, y) here u =velocity in x, v = velocity in y, p=pressure, x and y coordinates where y[0, ymax]. The boundary condition is described in “ON THE IMPLEMENTATION OF SYMMETRIC AND ANTISYMMETRIC PERIODIC BOUNDARY CONDITIONS FOR INCOMPRESSIBLE FLOW” by GUUS SEGAL, KEES VUIK AND KEES KASSELS. |
Cyclic boundary conditions can be used in this case.
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Quote:
yes they can, but then you need a cyclic geometry. Let me explain my case : I have a cubic domain which describe a porous media (liquid and solid). Only the liquid phase is meshed. Since the media is pretty random, the faces of my cube do not have the same mesh. To apply a cyclic boundary conditions (because that's what I want), I mirror the mesh in the x, y and finally z directions. I have then a cube 8 times bigger than my initial cube with all the same faces. I can then use cyclic boundary. But, I compute 7 times something I am not really interessted in. If I could apply antisymmetric periodicity, that would save a lot a time. Do you have any suggestions ? Fred. |
Hi Fredo,
What I do in this case: I had a thin layer of cells surrounding my domain. Like that I can impose cyclic boundary conditions. The two main problems when mirroring the domain: 1) it significantly increases the number of cells, 2) it biases the anisotropy (primordial for permeability estimation!). |
Hi Cyp,
thank you for this quick reply. Your solution seems very relevant ! Did you quantify the errors induced by this thin layer. My media is not very percolating so I fear that all the fluid goes through this thin layer. I will try and keep you updated. Fred. |
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