[Nek5000-users] Sponge/Dong boundary condition: Nek5000-users Digest, Vol 109, Issue 2

Mon Mar 12 11:17:20 CDT 2018

Hi Phillip,

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.

Thanks for your help.

Best,

Daniel

________________________________
From: Nek5000-users <nek5000-users-bounces at lists.mcs.anl.gov> on behalf of nek5000-users-request at lists.mcs.anl.gov <nek5000-users-request at lists.mcs.anl.gov>
Sent: 02 March 2018 18:00
To: nek5000-users at lists.mcs.anl.gov
Subject: Nek5000-users Digest, Vol 109, Issue 2

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Today's Topics:

   1. Re: Sponge layer in Nek5000 (nek5000-users at lists.mcs.anl.gov)
   2. Re: Sponge layer in Nek5000 (nek5000-users at lists.mcs.anl.gov)

----------------------------------------------------------------------

Message: 1
Date: Thu, 1 Mar 2018 12:24:45 -0700
From: nek5000-users at lists.mcs.anl.gov
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] Sponge layer in Nek5000
Message-ID:
        <mailman.9875.1519932288.19102.nek5000-users at lists.mcs.anl.gov>
Content-Type: text/plain; charset="utf-8"

Hi Daniel,

We did implement the Sponge layer a couple of years back in nek5000 at the
outflow boundary condition. We used a Smagorinsky type of eddy-viscosity
closure where the Smagorinsky coefficient quadratically varies in the x
direction (where is the direction of dominant flow), close to a few
elements near the outflow. You can set it up with uservp in nek5000.
However, the stabilized natural outflow boundary conditions by Dong et al.
(2014) behaves much better than the sponge layer in my opinion. For my type
of problem the sponge layer actually creates artificial diffusive
structures close to the boundary, even when they are applied very smoothly,
and you need to chop off the near-outflow region for data analysis.

On Thu, Mar 1, 2018 at 9:56 AM, <nek5000-users at lists.mcs.anl.gov> wrote:

> Hi all,
>
>
> I'm trying to implement outflow boundary conditions for a turbulent plume
> using a sponge layer to absorb the energy of the flow and prevent
> reflections back into the domain.  I was wondering whether there is
> anything set up in Nek already to construct this sponge layer or if it's
> something I need to do myself, and if so whether anybody could help with
> something they've done before - I've read a couple of other threads here
> that mention a sponge layer but not its implementation.
>
>
> I look forward to hearing from you.
>
>
> Best,
>
>
> Daniel Ward
>
> _______________________________________________
> Nek5000-users mailing list
> Nek5000-users at lists.mcs.anl.gov
> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>
>
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Message: 2
Date: Thu, 1 Mar 2018 22:05:45 +0100
From: nek5000-users at lists.mcs.anl.gov
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] Sponge layer in Nek5000
Message-ID:
        <mailman.9881.1519938356.19102.nek5000-users at lists.mcs.anl.gov>
Content-Type: text/plain; charset=utf-8; format=flowed

Hi,
we have also implemented various sponges and other boundary conditions,
including the Dong condition and convective conditions. The sponge we
typically base on a "direct" forcing approach as e.g. described in the
paper by Appelquist (JFM 2015); the implementation of that type of
forcing is in userf.

The Dong condition is essentially a modified "o" condition (where one
has to change a few lines here and there in the code, but I could send
you our code), and the convective condition, which behaved the best (see
e.g. the Master's thesis by Erik Bostr?m) can be implemented in
usercheck. The latter condition did create the least upstream disturbances.

Philipp

On 2018-03-01 20:24, nek5000-users at lists.mcs.anl.gov wrote:
> Hi Daniel,
>
> We did implement the Sponge layer a couple of years back in nek5000 at
> the outflow boundary condition. We used a Smagorinsky type of
> eddy-viscosity closure where the Smagorinsky coefficient quadratically
> varies in the x direction (where is the direction of dominant flow),
> close to a few elements near the outflow. You can set it up with uservp
> in nek5000. However, the stabilized natural outflow boundary conditions
> by Dong et al. (2014) behaves much better than the sponge layer in my
> opinion. For my type of problem the sponge layer actually creates
> artificial diffusive structures close to the boundary, even when they
> are applied very smoothly, and you need to chop off the near-outflow
> region for data analysis.
>
> On Thu, Mar 1, 2018 at 9:56 AM, <nek5000-users at lists.mcs.anl.gov
> <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>
>     Hi all,
>
>
>     I'm trying to implement outflow boundary conditions for a turbulent
>     plume using a sponge layer to absorb the energy of the flow and
>     prevent reflections back into the domain.? I was wondering whether
>     there is anything set up in Nek already to construct this sponge
>     layer or if it's something I need to do myself, and if so whether
>     anybody could help with something they've done before - I've read a
>     couple of other threads here that mention a sponge layer but not its
>     implementation.
>
>
>     I look forward to hearing from you.
>
>
>     Best,
>
>
>     Daniel Ward
>
>
>     _______________________________________________
>     Nek5000-users mailing list
>     Nek5000-users at lists.mcs.anl.gov <mailto:Nek5000-users at lists.mcs.anl.gov>
>     https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>     <https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users>
>
>
>
>
> _______________________________________________
> Nek5000-users mailing list
> Nek5000-users at lists.mcs.anl.gov
> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
>

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