[Nek5000-users] Turbulence Models not yet implemented

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

In turbChannel example. if param(30) = 1, then ifuservp is true, i.e., the
uservp subroutine is being called which allows you to use the user-defined
viscosity, in this case dynamic Smagorinsky based eddy viscosity.

Also, if param(30) = 0, nek5000 uses a filter-based model based on the
values of param(101), param(103). It is a little unconventional, but it can
also be treated as an LES model, damping out smaller scales of motion.

On Thu, Jul 7, 2016 at 10:35 AM, <nek5000-users at lists.mcs.anl.gov> wrote:

> I apologize, I wasn’t very clear in my previous message, at all.
>
>
>
> My question is this: there is a turbulent channel example included with
> Nek5000. According to the file turbChannel.usr, I have the understanding
> that this is an LES model of a turbulent channel at Re(tau)=590. How can
> this be an LES model if there are no turbulence models implemented in
> Nek5000?
>
>
>
> *From:* nek5000-users-bounces at lists.mcs.anl.gov [mailto:
> nek5000-users-bounces at lists.mcs.anl.gov] *On Behalf Of *
> nek5000-users at lists.mcs.anl.gov
> *Sent:* Thursday, July 07, 2016 11:11 AM
> *To:* nek5000-users at lists.mcs.anl.gov
> *Subject:* Re: [Nek5000-users] Turbulence Models not yet implemented
>
>
>
> Let me explain slightly better. For Direct Numerical Simulations (DNS),
> all the scales of turbulence are computed directly and no scales are
> modeled. Thus, no turbulence model is needed, you will get turbulence
> naturally as the direct solution of equations. Usually, some initial
> perturbation of the flow field is recommended to get the
> statistically-converged turbulence faster. For Large Eddy Simulations
> (LES), only the largest scales are computed directly, and the smaller
> scales are modeled (with the so-called sub grid-scale (SGS) models). SGS
> models for LES are available in Nek5000, including classical Smagorinsky
> and dynamic Smagorinsky models (they are in a TurbChannel example). For
> Reynolds Averaged Navier Stokes (RANS) simulations, all scales of motion
> are modeled. RANS models for Nek5000 are still in an exploratory stage and
> I believe are not yet part of the repo suite.
>
>
>
> Please, let me know if you have any further questions.
>
>
>
> Best regards,
>
> Yulia
>
>
>
> On Jul 6, 2016, at 4:42 PM, nek5000-users at lists.mcs.anl.gov wrote:
>
>
>
> I am trying to generate a set of DNS data for a turbulent channel flow,
> and I am currently trying to build my case in prex. When I try to select
> “Turbulence Model”, it says “Turbulence Models not yet implemented”. How
> can this be the case if there is already an example turbulent channel flow
> included with Nek5000?
>
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