[Nek5000-users] Small random perturbations

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

Hi,
indeed, the suggestions by Paul are probably the best way to get 
started! What we have experimented with was to use tripping also for 
periodic flows (i.e. a near-wall wall-normal focing); this way you do 
not really need to care about the divergence of the initial velocity 
field. This was quite useful for both pipes and ducts.

Philipp

On 2018-03-06 18:37, nek5000-users at lists.mcs.anl.gov wrote:
> 
> Dear Ali,
> 
> 
> I've had good luck for rapid transition to turbulence in pipes with the 
> attached i.c. routine.
> 
> 
> In addition to random perturbations, it has a significant amount stream 
> wise vorticity near the pipe wall that is rapidly stretched by the mean 
> shear profile, so it generally takes off fairly quickly (e.g., within 10 
> convective time units).
> 
> 
> Alternatively or in conjunction with this, you can start with a high 
> Reynolds number and then reduce the Re once turbulence has set in.
> 
> 
> hth,
> 
> Paul
> 
> 
> ------------------------------------------------------------------------
> *From:* Nek5000-users <nek5000-users-bounces at lists.mcs.anl.gov> on 
> behalf of nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
> *Sent:* Tuesday, March 6, 2018 10:09:35 AM
> *To:* nek5000-users at lists.mcs.anl.gov
> *Subject:* [Nek5000-users] Small random perturbations
> 
> Thank you for responding. It is axisymmetric with periodic conditions at 
> the ends.
> 
> 
> what geometry are you interested in?
> Philipp
> 
> On 2018-02-20 15:20,nek5000-users at lists.mcs.anl.gov 
> <https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users>  wrote:
>>//>/Hello everyone, />//>/    I am just wondering about the validity of my way to initiate />/turbulence. My question is that instead of introducing random />/disturbances to the initial velocity, can I introduce them to the />/pressure gradient? Hint, I am using Nek5000 to simulate statistically />/non-stationary turbulent flow. />//>/Thank you in advance />/Ali />/Embry-Riddle Aeronautical University/
> 
> 
> 
> 
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