Hi Justin, This is expected behaviour. Your attempt to impose a pressure BC using: dot(w,n)*patm*ds(6) will do nothing in the no-flow condition because the no-flow condition restricts the test space to the space for which dot(w, n) = 0. Your surface integral therefore contributes nothing to the form. I'm not even sure that the Stokes equations admit simultaneously specifying no flow and a fixed pressure. Intuitively, the no flow condition implies that the pressure rises at the boundary to the level required such that the pressure gradient normal to the boundary is zero and no flow results. Regards, David On Mon, 13 Feb 2017 at 07:25 Justin Chang <jychang48@gmail.com> wrote:

Hi again,

So this may or may not be related to the original issue. I was able to define corner IDs needed for my pressure BCs but I cannot seem to enforce both no-flow and atmospheric pressure simultaneously. Enforcing no-flow seems to negate the weakly prescribed pressure flux and my pressure solution is complete wack. On the otherhand, not enforcing no flow gives me a pressure profile I expect, but I no longer have a no flow domain.

Attached is my code, the custom boundary IDs begin at line 39, the weak formulations begin at line 164. Run the code as:

python 2D_Darcy_Homo_Iso.py 600 150 2

The code right now will generate a nonsensical pressure solution because I have no-flow enforced on all boundaries (including the corners).

Any ideas on what to do here?

Thanks, Justin

On Tue, Feb 7, 2017 at 4:55 AM, Lawrence Mitchell < lawrence.mitchell@imperial.ac.uk> wrote:

...

On 7 Feb 2017, at 09:03, Lawrence Mitchell < lawrence.mitchell@imperial.ac.uk> wrote:

PETSc.Options("foo_").getAll()

=> {"bar": "-baz_bar"}

I will push a fix for this one.

Please try the branch proposed here:

https://github.com/firedrakeproject/firedrake/pull/1004

Lawrence _______________________________________________ firedrake mailing list firedrake@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/firedrake

-- Dr David Ham Department of Mathematics Imperial College London