Ben,
Xujun and I work on particles in fluid -- point particles for now,
generalizing to colloidal suspensions (of extended particles later).
In particular Xujun has a few ideas for using enriched bases he wanted to
try. These may be related to the basis enrichment ideas we had discussed a
few months ago. We are sticking to libMesh for now, but once it starts
working it will be trivial to lift to MOOSE.
In our case the enrichment occurs at the nodes that are within a certain
radius of the (mobile) particles. I have a parallel particle tracking and
sorting code that I'm now cleaning up -- I should have an example ready to
push at the end of this weekend. It would be interesting to see how this
relates to the "ghost node" approach you are using for cracking.
Maybe we could set up a conference call to discuss these ideas?
Cheers,
Dmitry
PS.
Interestingly enough, even for point particles and even without XFEM we
already ran into a situation where we wanted to integrate over domains that
cut across mesh cells, so it would be interesting to see if we could use
Ben Kirk's code there and later for extended particles.
On Fri Nov 21 2014 at 4:00:50 PM Benjamin Spencer <benjamin.spen...@inl.gov>
wrote:
> On Fri, Nov 21, 2014 at 1:57 PM, Xujun Zhao <xzha...@gmail.com> wrote:
>
>> Thank you very much for those information. If this involves MOOSE, I
>> think I should bring Dmitry in :-)
>>
>
> Definitely. Are you working with him? We work with him quite a bit, and
> we've had some discussions on this topic in the past.
>
>
>> It seems both LibMesh and MOOSE are working to implement xfem on fracture
>> problems. Is this for dynamic cracks or just static ones? How about the
>> weak discontinuity problems, for example, material interfaces.
>>
>
> My work in MOOSE is focused on crack propagation. It's a dynamically
> changing crack topology, but it's not a dynamic problem in the sense of
> including the inertial terms in the solid mechanics PDEs. We don't really
> have good support for dynamic solid mechanics problems in MOOSE yet,
> although it's in the works. That won't really change much relative to
> XFEM, though.
>
> We haven't done anything for material interface problems, although we have
> some other problems of that nature that we'd like to use XFEM on.
>
> Ben Kirk can speak better to what he's doing in libmesh, but I think he's
> planning on using XFEM for moving shock fronts, and I think the main thing
> he's done at this point is implement a method for triangulation of the
> elements cut by those interfaces.
>
>
>> To Ben Spence:
>>
>> What does 'partial element' mean? is it the element cut by the
>> discontinuites or the sub-triangles after division for integration purpose?
>> Typically, numerical quadrature in those elements requires a nonlinear
>> mapping of quad points between two reference coordinates. One of the
>> possible ways to avoid nonlinear mapping is to use rational basis (shape
>> function).
>>
>
> We're using the phantom node approach of Hansbo and Hansbo, where the cut
> elements are replaced by two overlapping elements, each with a physical and
> a non-physical component. Those are what I refer to as partial elements.
> Ideally, we can just use the same integration points in the partial
> elements that we used before they were cut so we don't have to map anything.
>
> A. Hansbo and P. Hansbo. A finite element method for the simulation of
> strong and weak discontinuities in solid mechanics. CMAME,
> 193(33-35):3523–3540, 2004.
>
>
>>
>> On the other hand, how do you handle the hanging nodes for AMR in xfem?
>> Any problem?
>>
>
> I'm sure we will run into challenges using AMR with XFEM. It would be
> really cool to get the two working together, but we need to get the basics
> working first.
>
> -Ben
>
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