[firedrake] RT/BDM works but not TH/VMS

[Lawrence Mitchell]

> On 13 Nov 2015, at 20:34, Justin Chang <jychang48 at 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

Taylor hood is unstable for darcy, no? In which case it's not surprising it breaks. 

For you VMS formulation do you not also have to incorporate a piece in the RHS? Also, the formulations I have seen have opposite signs on the velocity trial and test functions in the stabilisation term. But I'm only passingly familiar, so take these comments with a pinch of salt. 

Lawrence 
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