[Nek5000-users] Small random perturbations

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

Dear Zhenrong,


Please send me your case files off-list, along with an explanation of how you start the case that re-laminarizes.


I'll try to sort this out.


Thanks!


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: Friday, March 16, 2018 3:22:07 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] Small random perturbations

Hello everyone

I have been troubled by the exactly same problem with Ali for the last two months with the turbulent channel case. When I increase elements, the flow is laminarized even though the Re is quite big (10000). I tried many different ways. Even added a constant random forcing, but the disturbance just disappear. (because the disturbance shape is not the same as that in linear stability theory, it is possible that the disturbance just decay. )

How I finally solve this problem is running a coarse mesh calculation first, and then interpolating the result to fine mesh. Then I got a sustaining turbulence and the result is quite satisfying. I hope this could solve Ali's problem.

However, I still cannot understand why increasing resolution would laminarize flow. hoping someone else could explain the problem.

Regards

Bien cordialement

Zhenrong JING

Doctorant (Doctor Candidate)

LHEEA

Ecole Centrale de Nantes

1 Rue de la Noë, 44321 Nantes, France
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