Hi Syavash,

Great, meanmode module would work on an averaged field.

If I were to understand the issue of “macro-elements on average RS” correctly, you are observing the footprint of the element edges on your RS field/plots. I’ve experienced similar issues before, and it fixed it by increasing spatial resolution. You might want to try increasing spatial resolution or extend time averaging. Good luck! 

Cheers
Chi Hin

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From: Ehsan Asgari <eh.asgari@gmail.com>
Sent: Friday, September 1, 2023 8:33:13 AM
To: Chan, Chi Hin <chi.chan19@imperial.ac.uk>
Cc: nektar-users <nektar-users@imperial.ac.uk>
Subject: Re: [Nektar-users] average planes in a quasi 3-D simulation
 
Thanks Chi Hin. This is very helpful.

Actually I needed spanwise- & time-averaged RS as you indicated. In fact, I was not sure if the meanmode filter would work on an average field (RS or mean velocity). 
A new issue is that I see footprints of macro-elements on the averaged RS, while the averaged velocity is conveniently smooth. 
Perhaps I should extend the averaging time to alleviate this effect. Do you have any suggestions?

Kind regards
syavash

On Fri, Sep 1, 2023 at 1:13 AM Chan, Chi Hin <chi.chan19@imperial.ac.uk> wrote:
Hi Syavash,

Yes, you are right. 

There's a ReynoldsStresses (RS) filter that computes the time-averaged RS. You could apply FieldConvert -m meanmode on the output .fld from the filter. 

Unfortunately, this process computes the spanwise- & time-averaged RS. I'm not entirely sure how to compute the spanwise-averaged, instantaneous RS if that's your goal.  Perhaps I could suggest tinkering with FieldConvert -m fieldfromstring (user guide v5.2) to create an instantaneous RS field manually.

Hope this helps.

Cheers,
Chi Hin
From: Ehsan Asgari <eh.asgari@gmail.com>
Sent: 31 August 2023 09:42
To: Chan, Chi Hin <chi.chan19@imperial.ac.uk>
Cc: nektar-users <nektar-users@imperial.ac.uk>
Subject: Re: [Nektar-users] average planes in a quasi 3-D simulation
 
Hi Chi Hin

Thanks for your reply. Yes I meant the spanwise averaging. But I guess this method would give a 2-D expansion containing the mean mode of instantaneous quantities.
What can I do if I'd also want to spanwise-average quantities such as Reynolds stresses?

Kind regards
syavash



On Thu, Aug 31, 2023 at 11:37 AM Chan, Chi Hin <chi.chan19@imperial.ac.uk> wrote:
Hi Syavash,

Are you referring to averaging across the homogeneous (z-th) direction? i.e the Fourier 0-th mode. 

If so, you can use FieldConvert -m meanmode. Hope this helps

Cheers
Chi Hin

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Subject: [Nektar-users] average planes in a quasi 3-D simulation
 

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Dear All,

How can I average the solutions of planes across the homogenous direction in a Quasi 3-D simulation?

Kind regards
syavash