dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

What happens when you run the same problem with first-order
stabilized? Same oscillations? What effect does the stabilization
parameter have?

/Anders


On Tue, May 23, 2006 at 11:16:15AM -0500, Robert C. Kirby wrote:
> Andy Terrel was doing some very basic Stokes flow with Taylor Hood  
> and getting some oscillations around the boundary.  I don't know how  
> to explain this behavior.
> 
> 
> On May 23, 2006, at 11:14 AM, Alexander Jarosch wrote:
> 
> >I use a direct solver and I have a boundary where the velocities =  
> >0 and on that boundary the pressure fluctuates even with a mixed  
> >Taylor-Hood approch.
> >
> >Alex
> >
> >Garth N. Wells wrote:
> >
> >>On Tue, 2006-05-23 at 14:46 +0000, Alexander Jarosch wrote:
> >>
> >>>Hi,
> >>>
> >>>did anyone play around with the stokes solver on more complex  
> >>>geometries?
> >>
> >>The demo in src/demo/pde/convection-diffusion solves the Stokes  
> >>problem
> >>around a dolphin using a Taylor-Hood element and the result looks OK.
> >>
> >>Garth
> >>
> >>
> >>
> >>>I only seem to get something senseful using a stabalized stokes  
> >>>like:
> >>>
> >>>scalar = FiniteElement("Lagrange", "triangle", 1)
> >>>vector = FiniteElement("Vector Lagrange", "triangle", 2)
> >>>system = vector + scalar
> >>>
> >>>(v, q) = TestFunctions(system)
> >>>(u, p) = TrialFunctions(system)
> >>>
> >>>f = Function(vector)
> >>>h = Function(scalar)
> >>>nu = Function(scalar)
> >>>
> >>>beta  = 0.2
> >>>delta = beta*h*h
> >>>
> >>>a = (nu*dot(grad(v), grad(u)) - div(v)*p + q*div(u) + delta*dot 
> >>>(grad(q), grad(p)))*dx
> >>>L = dot(v + mult(delta, grad(q)), f)*dx
> >>>
> >>>which is fine, but when I compare the solution to another FEM  
> >>>package, they do not quite match. Was there already some  
> >>>benchmarking done?
> >>>
> >>>cheers,
> >>>
> >>>Alex
> >>>
> >>
> >>
> >>
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> >>
> >>
> >
> >
> 
> 
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