[aspect-devel] internal velocity boundary conditions
jperryh2 at uoregon.edu
Tue May 12 17:49:53 PDT 2015
I actually had this on my list of hackathon items as well. It would be
On 05/12/2015 05:46 PM, Thorsten Becker wrote:
> Likewise not at the hackathon myself, but this exact application (for
> the Tohoku setting) would be of great interest to my group as well...
> Thorsten W Becker
> geodynamics.usc.edu <http://geodynamics.usc.edu/~becker>
> On Tue, May 12, 2015 at 5:43 PM, Magali Billen <mibillen at ucdavis.edu
> <mailto:mibillen at ucdavis.edu>> wrote:
> Hello Everyone,
> Unfortunately I’m not going to make it to Hackathon to ask this
> question in person, but this way everyone
> can read (ignore?) and hear or contribute to the response.
> The short form of my question is: Is it possible to define
> “internal” velocity boundary conditions in Aspect: that is
> can I fix the velocity at nodes inside the model domain? If the
> answer is yes, can someone comment on the basic steps
> that would be needed (e.g., need to flag these nodes as “boundary
> conditions” so they get handled properly during assembly of the
> solution matrices, then assign velocities,…).
> Here is the background for why I ask this question:
> One of the projects we are starting to develop in Aspect in my group
> is instantaneous models for a specific
> subduction zones. The key issue with these models is that we need to
> define a starting thermal structure
> that is based on the observed geometry of the subducted plate (e.g.,
> from seismicity). There are different
> was to do this, and I’ve done several of them for previous models
> completed using Citcom.
> Based on that experience, and given the AMR capabilities of Aspect,
> I think the best (most accurate and easiest) way to
> define the starting thermal structure is to run model in which you
> have defined the surface of the plate
> INSIDE the model (going down into the mantle) and then define fixed
> velocities associated with this surface.
> Note it is not necessary for the elements to conform to this surface
> (no distortion of the grid), we can use refinement of the grid to
> get accurate enough for our purposes.
> Once the velocity conditions inside the mesh are defined together
> with the normal external boundary conditions and an initial
> temperature structure for the plates at the actual top of the mesh,
> then we would run this model forward in time to kinematically
> “subduct” the plate. This will allow us to create a smooth 3D
> starting temperature models for our instantaneous dynamically-driven
> models that follows the observed shape of the slab.
> In addition to using this capability for the purpose describe above,
> this would allow Aspect to also run what is commonly referred to as
> “mantle wedge thermal models”, in which the subducted plate and
> overriding plates are really used as boundary conditions on the
> flow/temperature in the mantle between them. These models are
> commonly used to look at the detailed thermal structure and melting
> in the mantle wedge.
> Professor of Geophysics & UCD Chancellor Fellow
> Chair, Geology Graduate Program
> Earth & Planetary Sciences Dept., UC Davis
> Davis, CA 95616
> 2129 Earth & Physical Sciences Bldg.
> Office Phone: (530) 752-4169 <tel:%28530%29%20752-4169>
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