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<p style="margin-top:0;margin-bottom:0">Hi Phillip,</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">Apologies for the delayed reply, seeing your code and implementation of the Dong boundary condition would be very useful. I may also have a look at the Appelquist paper but at this point I would just like something that
allows my flow to leave the domain without crashing the simulation.</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">Thanks for your help.</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">Best,</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">Daniel<br>
</p>
<br>
<br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" color="#000000" face="Calibri, sans-serif"><b>From:</b> Nek5000-users <nek5000-users-bounces@lists.mcs.anl.gov> on behalf of nek5000-users-request@lists.mcs.anl.gov <nek5000-users-request@lists.mcs.anl.gov><br>
<b>Sent:</b> 02 March 2018 18:00<br>
<b>To:</b> nek5000-users@lists.mcs.anl.gov<br>
<b>Subject:</b> Nek5000-users Digest, Vol 109, Issue 2</font>
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Today's Topics:<br>
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1. Re: Sponge layer in Nek5000 (nek5000-users@lists.mcs.anl.gov)<br>
2. Re: Sponge layer in Nek5000 (nek5000-users@lists.mcs.anl.gov)<br>
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Message: 1<br>
Date: Thu, 1 Mar 2018 12:24:45 -0700<br>
From: nek5000-users@lists.mcs.anl.gov<br>
To: nek5000-users@lists.mcs.anl.gov<br>
Subject: Re: [Nek5000-users] Sponge layer in Nek5000<br>
Message-ID:<br>
<mailman.9875.1519932288.19102.nek5000-users@lists.mcs.anl.gov><br>
Content-Type: text/plain; charset="utf-8"<br>
<br>
Hi Daniel,<br>
<br>
We did implement the Sponge layer a couple of years back in nek5000 at the<br>
outflow boundary condition. We used a Smagorinsky type of eddy-viscosity<br>
closure where the Smagorinsky coefficient quadratically varies in the x<br>
direction (where is the direction of dominant flow), close to a few<br>
elements near the outflow. You can set it up with uservp in nek5000.<br>
However, the stabilized natural outflow boundary conditions by Dong et al.<br>
(2014) behaves much better than the sponge layer in my opinion. For my type<br>
of problem the sponge layer actually creates artificial diffusive<br>
structures close to the boundary, even when they are applied very smoothly,<br>
and you need to chop off the near-outflow region for data analysis.<br>
<br>
On Thu, Mar 1, 2018 at 9:56 AM, <nek5000-users@lists.mcs.anl.gov> wrote:<br>
<br>
> Hi all,<br>
><br>
><br>
> I'm trying to implement outflow boundary conditions for a turbulent plume<br>
> using a sponge layer to absorb the energy of the flow and prevent<br>
> reflections back into the domain. I was wondering whether there is<br>
> anything set up in Nek already to construct this sponge layer or if it's<br>
> something I need to do myself, and if so whether anybody could help with<br>
> something they've done before - I've read a couple of other threads here<br>
> that mention a sponge layer but not its implementation.<br>
><br>
><br>
> I look forward to hearing from you.<br>
><br>
><br>
> Best,<br>
><br>
><br>
> Daniel Ward<br>
><br>
> _______________________________________________<br>
> Nek5000-users mailing list<br>
> Nek5000-users@lists.mcs.anl.gov<br>
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Message: 2<br>
Date: Thu, 1 Mar 2018 22:05:45 +0100<br>
From: nek5000-users@lists.mcs.anl.gov<br>
To: nek5000-users@lists.mcs.anl.gov<br>
Subject: Re: [Nek5000-users] Sponge layer in Nek5000<br>
Message-ID:<br>
<mailman.9881.1519938356.19102.nek5000-users@lists.mcs.anl.gov><br>
Content-Type: text/plain; charset=utf-8; format=flowed<br>
<br>
Hi,<br>
we have also implemented various sponges and other boundary conditions, <br>
including the Dong condition and convective conditions. The sponge we <br>
typically base on a "direct" forcing approach as e.g. described in the <br>
paper by Appelquist (JFM 2015); the implementation of that type of <br>
forcing is in userf.<br>
<br>
The Dong condition is essentially a modified "o" condition (where one <br>
has to change a few lines here and there in the code, but I could send <br>
you our code), and the convective condition, which behaved the best (see <br>
e.g. the Master's thesis by Erik Bostr?m) can be implemented in <br>
usercheck. The latter condition did create the least upstream disturbances.<br>
<br>
Philipp<br>
<br>
On 2018-03-01 20:24, nek5000-users@lists.mcs.anl.gov wrote:<br>
> Hi Daniel,<br>
> <br>
> We did implement the Sponge layer a couple of years back in nek5000 at <br>
> the outflow boundary condition. We used a Smagorinsky type of <br>
> eddy-viscosity closure where the Smagorinsky coefficient quadratically <br>
> varies in the x direction (where is the direction of dominant flow), <br>
> close to a few elements near the outflow. You can set it up with uservp <br>
> in nek5000. However, the stabilized natural outflow boundary conditions <br>
> by Dong et al. (2014) behaves much better than the sponge layer in my <br>
> opinion. For my type of problem the sponge layer actually creates <br>
> artificial diffusive structures close to the boundary, even when they <br>
> are applied very smoothly, and you need to chop off the near-outflow <br>
> region for data analysis.<br>
> <br>
> On Thu, Mar 1, 2018 at 9:56 AM, <nek5000-users@lists.mcs.anl.gov <br>
> <<a href="mailto:nek5000-users@lists.mcs.anl.gov" id="LPlnk520606" previewremoved="true">mailto:nek5000-users@lists.mcs.anl.gov</a>>> wrote:<br>
> <br>
> Hi all,<br>
> <br>
> <br>
> I'm trying to implement outflow boundary conditions for a turbulent<br>
> plume using a sponge layer to absorb the energy of the flow and<br>
> prevent reflections back into the domain.? I was wondering whether<br>
> there is anything set up in Nek already to construct this sponge<br>
> layer or if it's something I need to do myself, and if so whether<br>
> anybody could help with something they've done before - I've read a<br>
> couple of other threads here that mention a sponge layer but not its<br>
> implementation.<br>
> <br>
> <br>
> I look forward to hearing from you.<br>
> <br>
> <br>
> Best,<br>
> <br>
> <br>
> Daniel Ward<br>
> <br>
> <br>
> _______________________________________________<br>
> Nek5000-users mailing list<br>
> Nek5000-users@lists.mcs.anl.gov <<a href="mailto:Nek5000-users@lists.mcs.anl.gov" id="LPlnk8260" previewremoved="true">mailto:Nek5000-users@lists.mcs.anl.gov</a>><br>
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