[Nek5000-users] Turbulence Models not yet implemented

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

Models typically "live" in the .usr file. There is no turbulence model in the code itself, except a legacy k-eps. Not sure if this implementation is up-to-date and well tested. 

> On 09.07.2016, at 18:03, nek5000-users at lists.mcs.anl.gov wrote:
> 
> 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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>>  
>> 
>> 
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