[aspect-devel] Aspect-devel Digest, Vol 61, Issue 4
Yimin Jin
choby1234567 at gmail.com
Fri Dec 9 18:53:42 PST 2016
Hi John,
Thanks for answering. It is inspiring to know that surface erosion models
have been implemented in ASPECT, but I still have some doubts: 1. The
adaptive refinements make the partition changes as the timestep goes on, so
if we use the function GridGenerator::extract_boundary_mesh() to extract
the surface mesh as an object of
parallel::distributed::Triangulation<dim-1,dim>, how can we keep the
partition of the surface mesh the same as the volume mesh? Or shall we
partition the two meshes independently and transport velocity data between
processes? 2. By saying 'I’m not sure what the status is of further
development pushing it to the main branch', did you mean that it is
difficult to merge this module to the program structure, or the surface
process module is not suitable to be added to ASPECT?
Cincerely,
Yimin Jin
2016-12-10 5:39 GMT+08:00 <aspect-devel-request at geodynamics.org>:
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> Today's Topics:
>
> 1. Re: Questions about surface process (John Naliboff)
> 2. Re: Van Keken et al. 2008 subduction benchmark (Max Rudolph)
> 3. Re: Van Keken et al. 2008 subduction benchmark
> (Thieulot, C.A.P. (Cedric))
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 9 Dec 2016 11:03:02 -0800
> From: John Naliboff <jbnaliboff at ucdavis.edu>
> To: aspect-devel at geodynamics.org
> Subject: Re: [aspect-devel] Questions about surface process
> Message-ID: <822D9590-B1B1-4FDB-96E4-E2BDF4B862E0 at ucdavis.edu>
> Content-Type: text/plain; charset="utf-8"
>
> Hi Yimin,
>
> I believe a number of people implemented a preliminary" diffusive" surface
> erosion model this summer. However, I’m not sure what the status is of
> further development pushing it to the main branch. Hopefully someone can
> chime in on this.
>
> Cheers,
> John
>
> *************************************************
> John Naliboff
> Assistant Project Scientist, CIG
> Earth & Planetary Sciences Dept., UC Davis
>
>
>
>
>
>
> > On Dec 9, 2016, at 2:30 AM, Yimin Jin <choby1234567 at gmail.com> wrote:
> >
> > Dear developers of ASPECT:
> >
> > I am a student of University of Chinese Academy of Sciences and I have
> been using ASPECT to do simulations on crack propagation of small-scaled
> geological bodies in the passing year. I have found that the existing
> velocity pojection strategies in the free-surface module introduces too
> much error to the result (the 'normal' strategy leads to severe distortion
> of cells, and the 'vertical' strategy ignores horizontal displacements),
> while the sticky-air method will double the computational complexity of the
> problem (my model can 'grow' tall so the air layer must be thick enough).
> Therefore I intended to apply a diffusive surface process on the
> free-surface, but when I looked into this problem I found it quite
> difficult because the partition changes each time we execute refinement and
> coarsening. The finest way seems to be transporting faces between processes
> using functions provided by p4est (I don't know if there are any), then it
> will be unavoidable to read the codes of p4est. Could you please tell me
> whether you have started to do such things or not? If it has been
> implemented and will soon be released, then I will be happily looking
> forward to the next version of ASPECT; otherwise, I would like to make my
> effort in this part of work.
> >
> > Cincerely,
> > Yimin Jin
> >
> > Key Laboratory of Computational Geodynamics, UCAS
> > _______________________________________________
> > Aspect-devel mailing list
> > Aspect-devel at geodynamics.org
> > http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel
>
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> ------------------------------
>
> Message: 2
> Date: Fri, 9 Dec 2016 11:12:13 -0800
> From: Max Rudolph <maxwellr at gmail.com>
> To: Scott King <sdk at vt.edu>
> Cc: aspect-devel <aspect-devel at geodynamics.org>
> Subject: Re: [aspect-devel] Van Keken et al. 2008 subduction benchmark
> Message-ID:
> <CAFNmARsEzxYJb6LbOW6s4EEsntcpCJFVgcCASsqCzBk9r8D5xw at mail.
> gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Scott and Wolfgang,
> I did not try the modification to allow a linear ramp. The problem that I
> encountered was not associated with the pressure field in the wedge. It was
> actually along the subduction interface where the downgoing plate meets the
> over-riding plate. There is a discontinuity in the velocity field there.
> The velocity field is locally divergence-free but it may not be
> divergence-free in the integral sense when interpolated using the finite
> element basis functions. One possible work-around would be to prescribe
> zero dynamic pressure throughout the rigid downgoing and over-riding plate
> (the correct solution). Doing so would mean prescribing all of the degrees
> of freedom for every node in the prescribed velocity region. I think that
> this would be a very straightforward modification of the prescribed
> velocity plugin. Maybe we can chat for a few minutes about this at the
> ASPECT dinner?
>
> Max
>
> On Fri, Dec 9, 2016 at 1:22 AM, Scott King <sdk at vt.edu> wrote:
>
> > Max;
> >
> > Do you use a linear ramp something from the point where the slab meets
> the
> > over-riding plate down into the wedge? This *smooths* the discontinuity
> > (at least as far as the wedge sees it). With this the pressure fields in
> > the wedge seems to become more smooth for many codes. I always had to
> you
> > a much larger "ramp" (25,-50 km) because my elements were not refined as
> > much as Herr. Dr. Prof. van Keken. This puts the discontinuity into the
> > part of the domain where the velocities are entirely prescribed. It
> seems
> > to be ok for some codes because they don't "solve" any equation when all
> > the velocities are prescribed. Years of arguing and twiddling.
> >
> > Scott
> >
> > On Dec 8, 2016, at 10:25 PM, Wolfgang Bangerth <bangerth at tamu.edu>
> wrote:
> >
> > > On 10/27/2016 10:13 AM, Max Rudolph wrote:
> > >> I was wondering if anyone has been successful in setting up the Van
> > Keken et
> > >> al. 2008 subduction benchmark using ASPECT? I have been using this as
> a
> > >> starting point to set up a more complicated corner flow model and have
> > not yet
> > >> been successful.
> > >>
> > >> This benchmark solution requires a rigid overriding plate and
> kinematic
> > >> subducting plate. There is a discontinuity along the subduction
> > interface. I
> > >> tried imposing kinematic boundary conditions on the left and bottom of
> > the box
> > >> and using Jonathan Perry-Houts' prescribed velocity plugin
> > >> (cookbooks/prescribed_velocity), but the Stokes solver fails to
> > converge.
> > >> Looking at the pressure field, it's not surprising to see very large
> > >> oscillations in this region where the velocity field is discontinuous.
> > It
> > >> occurred to me that using the locally conservative discretization
> might
> > help.
> > >> However, when the locally conservative discretization is enabled, the
> > internal
> > >> prescribed velocities are no longer enforced anywhere. Is it obvious
> > why this
> > >> might be the case?
> > >
> > > Max -- I haven't tried implementing the benchmark in ASPECT, but recall
> > trying to do so in an early version of step-32 when I visited Scott in
> > Blacksburg for the very first time many many years ago. I remember it to
> be
> > very difficult because the benchmark definition really doesn't fit the
> > finite element method.
> > >
> > > One of the issues with the use of the prescribed velocity is that the
> > prescribed velocity needs to be divergence free on each cell. Is it, in
> > your case? Even on cells where you only prescribe values at some nodes?
> > >
> > > Best
> > > W.
> > >
> > > --
> > > ------------------------------------------------------------
> ------------
> > > Wolfgang Bangerth email:
> bangerth at colostate.edu
> > > www: http://www.math.colostate.edu/
> ~bangerth/
> > >
> > > _______________________________________________
> > > Aspect-devel mailing list
> > > Aspect-devel at geodynamics.org
> > > http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel
> >
> >
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> ------------------------------
>
> Message: 3
> Date: Fri, 9 Dec 2016 21:32:48 +0000
> From: "Thieulot, C.A.P. (Cedric)" <c.thieulot at uu.nl>
> To: "maxwellr at gmail.com" <maxwellr at gmail.com>,
> "aspect-devel at geodynamics.org" <aspect-devel at geodynamics.org>
> Subject: Re: [aspect-devel] Van Keken et al. 2008 subduction benchmark
> Message-ID: <FB2A0542-6101-4613-B2BA-AB5BB4EED818 at uu.nl>
> Content-Type: text/plain; charset="windows-1252"
>
> hi,
> I believe that Scott’s advice still holds: if you look at subsection 2.3
> of the paper, you’ll see that along the interface
> between downgoing plate and overriding place there is no velocity
> discontinuity.
> Ce/
>
>
>
>
> [cid:83FFAEC2-5940-4970-B26E-88C7176B394B at lan]
>
> On 09 Dec 2016, at 20:12, Max Rudolph <maxwellr at gmail.com<mailto:max
> wellr at gmail.com>> wrote:
>
> Scott and Wolfgang,
> I did not try the modification to allow a linear ramp. The problem that I
> encountered was not associated with the pressure field in the wedge. It was
> actually along the subduction interface where the downgoing plate meets the
> over-riding plate. There is a discontinuity in the velocity field there.
> The velocity field is locally divergence-free but it may not be
> divergence-free in the integral sense when interpolated using the finite
> element basis functions. One possible work-around would be to prescribe
> zero dynamic pressure throughout the rigid downgoing and over-riding plate
> (the correct solution). Doing so would mean prescribing all of the degrees
> of freedom for every node in the prescribed velocity region. I think that
> this would be a very straightforward modification of the prescribed
> velocity plugin. Maybe we can chat for a few minutes about this at the
> ASPECT dinner?
>
> Max
>
> On Fri, Dec 9, 2016 at 1:22 AM, Scott King <sdk at vt.edu<mailto:sdk at vt.edu>>
> wrote:
> Max;
>
> Do you use a linear ramp something from the point where the slab meets the
> over-riding plate down into the wedge? This *smooths* the discontinuity
> (at least as far as the wedge sees it). With this the pressure fields in
> the wedge seems to become more smooth for many codes. I always had to you
> a much larger "ramp" (25,-50 km) because my elements were not refined as
> much as Herr. Dr. Prof. van Keken. This puts the discontinuity into the
> part of the domain where the velocities are entirely prescribed. It seems
> to be ok for some codes because they don't "solve" any equation when all
> the velocities are prescribed. Years of arguing and twiddling.
>
> Scott
>
> On Dec 8, 2016, at 10:25 PM, Wolfgang Bangerth <bangerth at tamu.edu<mailto:
> bangerth at tamu.edu>> wrote:
>
> > On 10/27/2016 10:13 AM, Max Rudolph wrote:
> >> I was wondering if anyone has been successful in setting up the Van
> Keken et
> >> al. 2008 subduction benchmark using ASPECT? I have been using this as a
> >> starting point to set up a more complicated corner flow model and have
> not yet
> >> been successful.
> >>
> >> This benchmark solution requires a rigid overriding plate and kinematic
> >> subducting plate. There is a discontinuity along the subduction
> interface. I
> >> tried imposing kinematic boundary conditions on the left and bottom of
> the box
> >> and using Jonathan Perry-Houts' prescribed velocity plugin
> >> (cookbooks/prescribed_velocity), but the Stokes solver fails to
> converge.
> >> Looking at the pressure field, it's not surprising to see very large
> >> oscillations in this region where the velocity field is discontinuous.
> It
> >> occurred to me that using the locally conservative discretization might
> help.
> >> However, when the locally conservative discretization is enabled, the
> internal
> >> prescribed velocities are no longer enforced anywhere. Is it obvious
> why this
> >> might be the case?
> >
> > Max -- I haven't tried implementing the benchmark in ASPECT, but recall
> trying to do so in an early version of step-32 when I visited Scott in
> Blacksburg for the very first time many many years ago. I remember it to be
> very difficult because the benchmark definition really doesn't fit the
> finite element method.
> >
> > One of the issues with the use of the prescribed velocity is that the
> prescribed velocity needs to be divergence free on each cell. Is it, in
> your case? Even on cells where you only prescribe values at some nodes?
> >
> > Best
> > W.
> >
> > --
> > ------------------------------------------------------------------------
> > Wolfgang Bangerth email: bangerth at colostate.edu
> <mailto:bangerth at colostate.edu>
> > www: http://www.math.colostate.edu/~bangerth/
> >
> > _______________________________________________
> > Aspect-devel mailing list
> > Aspect-devel at geodynamics.org<mailto:Aspect-devel at geodynamics.org>
> > http://lists.geodynamics.org/cgi-bin/mailman/listinfo/aspect-devel
>
>
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