I originally solve that example problem using LU. But when I solve this one:
http://fenicsproject.org/documentation/dolfin/1.5.0/python/demo/documented/stokes-iterative/python/documentation.html
By simply running their code as is for TH and adding the one like I
mentioned for MTH, I get the
Lawrence Mitchell lawrence.mitch...@imperial.ac.uk writes:
Maybe Justin can chime in here, I don't know, I just happened to know
how the fenics implementation produces the basis, so proffered that.
Thanks, Lawrence. Unfortunately, my original questions remain
unanswered and now I'm doubly
MTH did not converge with the default -ksp_rtol 1e-6 so I had to raise the
tolerance to 1e-5 in order to get a solution. Attached are the outputs for
TH and MTH
Last one with the svd did not work with the way the AMG PC was hard-coded
into FEniCS. Here's the list of preconditioners my
Justin Chang jychan...@gmail.com writes:
I originally solve that example problem using LU.
I'd like to learn why LU didn't notice that the system is singular.
(The checks are not reliable, but this case should be pretty obviously
bad.)
But when I solve this one:
On Tue, Jun 2, 2015 at 4:00 PM, Justin Chang jychan...@gmail.com wrote:
MTH did not converge with the default -ksp_rtol 1e-6 so I had to raise the
tolerance to 1e-5 in order to get a solution. Attached are the outputs for
TH and MTH
This really looks like it was never solving this system.
Justin Chang jychan...@gmail.com writes:
Last one with the svd did not work with the way the AMG PC was hard-coded
into FEniCS. Here's the list of preconditioners my installation of FEniCS
supports:
Preconditioner| Description
On Tue, Jun 2, 2015 at 6:13 AM, Justin Chang jychan...@gmail.com wrote:
In FEniCS's Stokes example (example 19), one defines the Taylor-Hood
function spaces with these three lines:
V = VectorFunctionSpace(mesh, CG, 2)
Q = FunctionSpace(mesh, CG, 1)
W = V * Q
To implement P2/(P1+P0), all
On Mon, Jun 1, 2015 at 9:51 PM, Justin Chang jychan...@gmail.com wrote:
Jed,
I am not quite sure what you're asking for. Are you asking for how people
actually implement this augmented TH? In other words, how the shape/basis
functions for this mixed function space would look? I have only
On Tue, Jun 2, 2015 at 7:18 AM, Lawrence Mitchell
lawrence.mitch...@imperial.ac.uk wrote:
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On 02/06/15 13:14, Matthew Knepley wrote:
On Tue, Jun 2, 2015 at 6:13 AM, Justin Chang jychan...@gmail.com
mailto:jychan...@gmail.com wrote:
In
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On 02/06/15 13:37, Matthew Knepley wrote:
This construction appears to throw away unisolvence.
Yes, it's normally used for building spaces where the resulting
enriched space is unisolvent (e.g. MINI).
In the Boffi paper, they use QR to solve
Lawrence Mitchell lawrence.mitch...@imperial.ac.uk writes:
So-called enriched elements in FEniCS are not created with a nodal
basis, instead te basis for the space Q + P is just the
concatenation of the bases for Q and P separately and so tabulation of
basis functions at points is just the
Lawrence Mitchell lawrence.mitch...@imperial.ac.uk writes:
So the mass matrix for CG1+DG0 is singular?
I believe so, yes.
Fabulous. Now let's take a one element domain. What is the norm of the
vector
u=((1,1,1),(-1))
in the basis {CG1, DG0}? Note that this represents the continuous
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On 02/06/15 17:20, Jed Brown wrote:
Lawrence Mitchell lawrence.mitch...@imperial.ac.uk writes:
So the mass matrix for CG1+DG0 is singular?
I believe so, yes.
Fabulous. Now let's take a one element domain. What is the norm
of the vector
There are a few papers that discuss this modified/augmented Taylor-Hood
elements for Stokes equations in detail (e.g.,
http://link.springer.com/article/10.1007%2Fs10915-011-9549-4). From what I
have seem, it seems people primarily use this to ensure local mass
conservation while attaining the
On Mon, Jun 1, 2015 at 9:38 AM, Jed Brown j...@jedbrown.org wrote:
Justin Chang jychan...@gmail.com writes:
There are a few papers that discuss this modified/augmented Taylor-Hood
elements for Stokes equations in detail (e.g.,
http://link.springer.com/article/10.1007%2Fs10915-011-9549-4).
Justin Chang jychan...@gmail.com writes:
There are a few papers that discuss this modified/augmented Taylor-Hood
elements for Stokes equations in detail (e.g.,
http://link.springer.com/article/10.1007%2Fs10915-011-9549-4).
This analysis does not state a finite element.
From what I have
Jed,
I am not quite sure what you're asking for. Are you asking for how people
actually implement this augmented TH? In other words, how the shape/basis
functions for this mixed function space would look? I have only seen in
some key note lectures and presentations at conferences briefly
Justin Chang jychan...@gmail.com writes:
I am referring to P2 / (P1 + P0) elements, I think this is the correct way
of expressing it. Some call it modified Taylor Hood, others call it
something else, but it's not Crouzeix-Raviart elements.
Okay, thanks. This pressure space is not a disjoint
Justin Chang jychan...@gmail.com writes:
Hello everyone,
In SNES ex62, it seems to solve the Stokes equation using TH elements
(i.e., using P2-P1 elements). However, this formulation is not locally
conservative, and as a result many people use the P2-P1/P0 elements where
the pressure space
I am referring to P2 / (P1 + P0) elements, I think this is the correct way
of expressing it. Some call it modified Taylor Hood, others call it
something else, but it's not Crouzeix-Raviart elements.
On Sat, May 30, 2015 at 8:28 PM, Jed Brown j...@jedbrown.org wrote:
Justin Chang
Hello everyone,
In SNES ex62, it seems to solve the Stokes equation using TH elements
(i.e., using P2-P1 elements). However, this formulation is not locally
conservative, and as a result many people use the P2-P1/P0 elements where
the pressure space is enriched with a piece-wise constant to
On Sat, May 30, 2015 at 2:37 AM, Justin Chang jychan...@gmail.com wrote:
Hello everyone,
In SNES ex62, it seems to solve the Stokes equation using TH elements
(i.e., using P2-P1 elements). However, this formulation is not locally
conservative, and as a result many people use the P2-P1/P0
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