[CIG-SHORT] pylith time stepping
Brad Aagaard
baagaard at usgs.gov
Tue May 12 11:58:28 PDT 2009
Chris-
I will add a test case for this and trap the error.
Brad
Christopher DiCaprio wrote:
> It looks like the problem with the data files occurs when
> total_time / max_dt < output.skip
>
> - Chris
>
>
> On May 12, 2009, at 6:45 AM, Brad Aagaard wrote:
>
>> Chris-
>>
>> As Charles noted, the time step for the Maxwell model is independent
>> of the deformation rate, so the adaptive time step is uniform. It does
>> depend on the Maxwell time. The time step for an elastic material is
>> infinite (actually 1.0e+30); any time step gives a numerically stable
>> solution. If you use an elastic material with adaptive time stepping,
>> the time step is 1.0e+30, so the number of time steps is being rounded
>> off to 0. The output manager currently uses the number of time steps
>> as a flag to decide whether it is writing "info" or "data". If the
>> number of time steps is 0, it thinks it is writing "info".
>>
>> The adaptive time stepping correctly writes "data" files when using a
>> Maxwell model. See examples/3d/hex8/savageprescott.cfg.
>>
>> Brad
>>
>>
>> Charles Williams wrote:
>>> At present, the automatic time stepping is controlled purely by the
>>> Maxwell time (for viscoelastic materials). Since the current
>>> viscoelastic materials are all linear, the time step size is
>>> independent of the deformation rate. Once we include nonlinear
>>> materials (e.g, power-law rheology), this will no longer be true.
>>> We will have to look at the second thing you mention. I don't think
>>> we had noticed that before.
>>> Thanks,
>>> Charles
>>> On 12/05/2009, at 3:55 PM, Christopher DiCaprio wrote:
>>>> Hi,
>>>>
>>>> It's not clear to me what is supported for the nonuniform,
>>>> automatic time stepping. The release notes for 1.3.0 say "For the
>>>> current bulk constitutive models, the automatically determined time
>>>> step is independent of the deformation rate, so it is uniform."
>>>>
>>>> The release notes for 1.3.1 don't mention time stepping, but the
>>>> manual implies that there is support for non-uniform time steps.
>>>>
>>>> One other thing: when using nonuniform, automatic time stepping,
>>>> the *_info.vtk files are overwritten with what should go in the
>>>> *_t0000.vtk files. This doesn't happen when using user-specified
>>>> time stepping.
>>>>
>>>> Thanks,
>>>> Chris
>>>>
>>>>
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>>> Charles A. Williams
>>> Scientist
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>>
>
>
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