[aspect-devel] Evenly spaced vectors, dynamic pressure

[Adam Holt]

Great! This indeed gives a reference profile closer to hydrostatic (resulting in lateral pressure gradients being clear in the "nonadiabatic pressure").

Thanks for the tip Rene, and thanks Wolfgang for the clarification (previous email)

-Adam

________________________________________
From: Aspect-devel [aspect-devel-bounces at geodynamics.org] on behalf of Rene Gassmoeller [rene.gassmoeller at mailbox.org]
Sent: Friday, September 07, 2018 6:50 PM
To: aspect-devel at geodynamics.org
Subject: Re: [aspect-devel] Evenly spaced vectors, dynamic pressure

Hi Adam,

If your nonadiabatic pressure is dominated by a 1D trend that likely
means the reference profile that is computed by ASPECT in the
initialization is not quite consistent with the actual pressure solution
in your model. You can control the reference profile that is computed by
setting the following parameters in the parameter file:

set Surface pressure = 0
set Adiabatic surface temperature = 0 (change to whatever temperature
you use as reference temperature in the material model)

That might not totally eliminate the deviation between reference profile
and hydrostatic pressure, but it should help a great deal.

Best,

Rene


On 09/07/2018 10:42 AM, Adam Holt wrote:
> Thanks much for the explanation! I'm interested in the component of the pressure that drives flow, so yes it sounds like this "nonadiabatic pressure". (For my incompressible models, I'm assuming this is just total minus hydrostatic pressure.)
>
> I was confused because the "nonadiabatic pressure" output is dominated by a depth-dependent 1-D trend.  I'm assuming this is a numerical/normalization thing, and I just need to remove the horizontal average at all depths.
>
> many thanks,
> Adam
>
>
> ________________________________________
> From: Aspect-devel [aspect-devel-bounces at geodynamics.org] on behalf of Wolfgang Bangerth [bangerth at colostate.edu]
> Sent: Thursday, September 06, 2018 11:20 PM
> To: aspect-devel at geodynamics.org
> Subject: Re: [aspect-devel] Evenly spaced vectors, dynamic pressure
>
> On 09/06/2018 01:25 PM, Adam Holt wrote:
>> Second, I am interested in the dynamic pressure field and wondered how best
>> to retrieve it from my (incompressible) models. For such models, I assume
>> it can be computed by subtracting the horizontally-constant static pressure
>> from the pressure outputted (the 'nonadiabatic pressure' output variable).
> I think that the "nonadiabatic pressure" is exactly the "dynamic pressure" you
> want: it's the total pressure minus the adiabatic pressure. So there isn't a
> need to write anything new, you just need to specify "nonadiabatic pressure"
> in the list of visualization variables.
>
> Though it is true that the adiabatic pressure is only computed once at the
> beginning of a simulation, and is not equal to the horizontally averaged
> pressure. There are, in other words, multiple ways to define a "dynamic
> pressure", and you need to specify which one exactly you want in order to
> figure out whether there is already an existing visualization postprocessor.
>
> Cheers
>    W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth          email:                 bangerth at colostate.edu
>                              www: http://www.math.colostate.edu/~bangerth/
>
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--
Rene Gassmoeller
https://gassmoeller.github.io/

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