[Nek5000-users] Sponge layer in Nek5000

[nek5000-users at lists.mcs.anl.gov]

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
>
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