Silly me

For VMS and TH I had to apply the homogeneous boundary conditions strongly. TH is stable, at least from my experience (although not preferred since it is not mass conservative). And yes I wrote the VMS formulation incorrectly, there is a minus sign indeed.

Thanks,

Justin

On Fri, Nov 13, 2015 at 3:07 PM, Lawrence Mitchell <lawrence.mitchell@imperial.ac.uk> wrote:

On 13 Nov 2015, at 20:34, Justin Chang <jychang48@gmail.com> wrote:

V = VectorFunctionSpace(mesh,"CG",1)
Q = FunctionSpace(mesh,"CG",1)
W = V*Q
v,p = TrialFunctions(W)
w,q = TestFunctions(W)
...
a = (dot(v, w) - p*div(w) - div(v)*q)*dx + 0.5*dot(v+grad(p),w+grad(q))*dx
L = f*q*dx

if that's what you're asking

Plausibly also your boundary conditions are not applied correctly.

In the hdiv-L2 formulation I would apply the pressure bcs weakly. But they're homogeneous, so those surface integral a vanish. Because the spaces match correctly this is enough. In the TH or VMS formulation to you have to explicitly apply the bcs strongly to the pressure variable?

Lawrence

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