[Nek5000-users] Mesh optimisation for the cylinder case ext_cyl

Tue May 22 08:50:41 CDT 2018

Dear Alexis,

The ext_cyl demo was an early example of start-to-finish meshing for

flow past a cylinder.

It's certainly not the case that it is optimized---users have many options for

building meshes that are optimized for their particular flow conditions as

the elements may be connected in any unstructured way.

We also have new mesh smoothing tools and a nonconforming overlapping

domain capability that would allow for a fine mesh in the cylinder and cylinder

wake with a relatively coarse mesh in the far field.

hth,

Paul

________________________________
From: Nek5000-users <nek5000-users-bounces at lists.mcs.anl.gov> on behalf of nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
Sent: Tuesday, May 22, 2018 2:21:32 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] Mesh optimisation for the cylinder case ext_cyl

Dear Nek5000 masters,

I have been able to run the ext_cyl example. And, after postprocessing the case, it made me wonder if Nek5000 is able to run this case with a more optimized mesh? That is, refined just close to the cylinder and coarse away from it.

Clearly, for this case, the refinement around the cylinder extends in sort of a “+” shape away from the cylinder. This refinement away from the cylinder is not necessary, specially towards the sides and towards the upstream. But even in the downstream the mesh could be (ideally) a bit coarser.

Some other CFD codes are able to handle this problem by accepting refinement of the mesh just close to the cylinder (obviously at the surface of the refinement an element from the coarser side becomes neighbour of two or more elements on the refined side). I’m wondering if Nek5000 is already capable of handling this kind of refinement (or possibly any other solution/trick {maybe lowering the order of the elements themselves}) in order to avoid this typical problem of excessive refinement where it’s not needed/desired?

Wondering and hoping, indeed, because this problem may become serious for some other configurations, for example for an array of cylinders, which then my cause the mesh to be refined all over the domain and not just in the “+” shape region.

Thanks a lot,

Alexis

Dr Alexis Espinosa

Supercomputing Specialist

Pawsey Supercomputing Centre

26 Dick Perry Ave

Kensington  WA  6151

Australia

Tel  +61 xxxx xxxx

Email  alexis.espinosa at pawsey.org.au<mailto:alexis.espinosa at pawsey.org.au>

Web  www.pawsey.org.au<http://www.pawsey.org.au/>

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From: Alexis Espinosa Gayosso <alexis.espinosa at pawsey.org.au>
Date: Tuesday, 8 May 2018 at 4:46 pm
To: <nek5000-users at lists.mcs.anl.gov>
Subject: Compiling Problems in "Running your very first simulation"

Hello,

The title of my thread is the same as for an already existing thread (26-Sept-2017) because:

I receive very similar warning messages when compiling nek5000 (./maketools all). Lots of warnings!

>From your answer on that thread it seems that you do not worry at all for the warning messages. Should we really not care about them? How to know which warnings are not of concern and which other are? Can you post your own .log file to see which warning messages are considered normal for you? Or how do you check everything went fine for the compilation?

Anyway, I will start running the examples in order to learn about the usage of the code. And I guess any abnormality would appear there.

Many thanks,

Alexis

Dr Alexis Espinosa

Supercomputing Specialist

Pawsey Supercomputing Centre

26 Dick Perry Ave

Kensington  WA  6151

Australia

Tel  +61 xxxx xxxx

Email  alexis.espinosa at pawsey.org.au<mailto:alexis.espinosa at pawsey.org.au>

Web  www.pawsey.org.au<http://www.pawsey.org.au/>

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