[aspect-devel] temperature anomaly postprocessor

[Max Rudolph]

Wolfgang,
Alternatively, how about this approach, which would avoid modifying all of
the other postprocessor classes.
I could add a private variable to the temperature anomaly class that
checked the current timestep number, and if it was not the current step,
update the depth average values. I think that this could be done within the
simpler interface to DataPostprocessorScalar.

Max

On Mon, Jul 9, 2018 at 1:25 PM Max Rudolph <maxrudolph at ucdavis.edu> wrote:

> Wolfgang,
> Thank you for your response!
>
> On Mon, Jul 9, 2018 at 12:37 PM Wolfgang Bangerth <bangerth at colostate.edu>
> wrote:
>
>>
>> Hi Max,
>>
>> > I want to be able to be able to output the temperature anomaly
>> > (temperature-average temperature at this depth). It looks like there
>> are some
>> > postprocessors that do similar things but nothing exactly like this.
>> For
>> > instance, the temperature-adiabatic temperature is similar, but not
>> applicable
>> > to an incompressible model, and only of limited relevance to
>> understanding the
>> > buoyancy structure in a compressible model. I do not see a way to do
>> this in
>> > VisIt either. Please let me know if this functionality already exists!
>> >
>> > I have a question about how to implement such a postprocessor. I think
>> that
>> > what I need to do is first calculate a depth-averaged temperature
>> (similar to
>> > the calculation of depth-averaged Vs in seismic anomalies.cc) and then
>> > calculate and subtract the depth-average value from each temperature
>> value.
>>
>> Yes, this sounds correct.
>>
>>
>> > If I make a new postprocessor that inherits from
>> DataPostprocessorScalar, my
>> > understanding is that evaluate_vector_field gets called on each cell,
>> so if I
>> > call get_lateral_averaging().get_temperature_averages() from within
>> this
>> > function, the code will be exceedingly slow as the depth averages would
>> be
>> > re-calculated for every cell. The only way that I can see to get around
>> this
>> > would be to calculate the depth-averaged temperature once in the
>> 'Initialize'
>> > method of my postprocessor. Do postprocessors get re-initialized each
>> > timestep? If not, this would not work.
>>
>> I don't think this is happening. The function that does this at each time
>> step
>> for other plugins is called 'update()', but it seems like the interface
>> for
>> visualization postprocessors does not have such a function, and in any
>> case I
>> don't see it called. It would not be terribly difficult to add, though.
>>
>
> I think that adding such a function is probably the best approach. Right
> now, if you wanted to, for instance, save depth averages, calculate a
> temperature anomaly, and calculate seismic velocities, the depth average
> postprocessor would be called three times. If instead there were a way to
> ensure that the depth averages had been updated for the current timestep
> and then simply retrieve them as needed, this would be ideal. I would
> prefer I guess to add an .update() function to the postprocessors. I would
> also modify the depth_averages postprocessor so that it will return a 1D
> interpolating function that can be queried similar to
> .get_temperature_averages() but perhaps .get_temperature_at_depth(double
> depth). Does this seem OK?
>
>
>> > The other possibility seems to be to write something that inherits from
>> > SimulatorAccess and CellDataVectorCreator, but then I will only get an
>> average
>> > temperature for each cell, which is not what I would prefer. Is there
>> > something like CellDataVectorCreator that works with nodal values
>> instead of
>> > cell-centered values?
>>
>> No. But you found what I would have suggested. The SeismicV*Anomalies
>> classes
>> do what you suggest, and would serve as an example to start from. If your
>> mesh
>> is fine enough, then the piecewise constant approximation is probably
>> pretty
>> good. The only thing you can't do with it is to plot
>> isocontours/surfaces. Is
>> that what you're after?
>>
>
> I want to be able to plot the actual buoyancy structure, so need to
> calculate either temperature-mean temperature or density-mean density. I
> guess that 'plan C' would be to write some scripts that read the depth
> averages and .vtu or .h5 files and calculate the desired quantity as a
> post-processing step but this seems inefficient.
>
>
>> Best
>>   W.
>>
>> --
>> ------------------------------------------------------------------------
>> Wolfgang Bangerth          email:                 bangerth at colostate.edu
>>                             www: http://www.math.colostate.edu/~bangerth/
>>
>>
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