[Nek5000-users] Small random perturbations
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Wed Mar 7 00:10:49 CST 2018
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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