Yes, this is more clear! :) Xujun
On Fri, Nov 21, 2014 at 4:46 PM, Dmitry Karpeyev <karp...@mcs.anl.gov>
wrote:
> 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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