Post #2870363
2026-04-16 14:54 UTC
@matt_zucker@mastodon.social I think I understand the periodic boundary condition -- it uses a fixed set of grid squares just outside the tile, used to calculate diffusion. Right?
But how do you put a grid on a regular pentagon? If it's an irregular grid, how do you calculate the Laplacian? It seems like diffusion rate would become direction-dependent.
Thanks.
Replies (1)
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@matt_zucker@mastodon.social 2026-04-16 21:43
@kbob@chaos.social For PBC on a square grid you can use an extra layer of grid squares outside the tile, but they are not fixed – they copy values from the opposite side of the domain. See e.g. page 3 of https://www.josstam.com/_files/ugd/cf1fd6_9989229efbd34a26ba5ccd913721a2ac.pdf. But I'm not using square grids - that would be the finite difference method. Instead I use triangle meshes with the finite element method. Much better for shapes like pentagons with no right angles.