[Nek5000-users] problem with turbCahnnel case
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Tue Jun 22 09:10:18 CDT 2010
Thank you Paul,
I run on 16 processors.
I run the channel for much longer and I confirm that the periodicity starts to disappear at about time=65.
Thank you
francesco
-----Original Message-----
From: nek5000-users-bounces at lists.mcs.anl.gov on behalf of nek5000-users at lists.mcs.anl.gov
Sent: Tue 6/22/2010 2:29 PM
To: nek5000-users at lists.mcs.anl.gov
Subject: Re: [Nek5000-users] problem with turbCahnnel case
PS - note that you can circumvent the P-dependency
by using a random number generator that is based
on a P-independent generator. There is an example
in the rayleigh/ray0.usr file in useric().
On Tue, 22 Jun 2010, nek5000-users at lists.mcs.anl.gov wrote:
>
> Dear Francesco,
>
> Are you using 4 processors (or perhaps 8?)
>
> My guess is that the periodicity you're seeing is the imprint
> of the rand1 function on the initial conditions, which is not
> really random in this case since it gives the same result for
> each processor. Hence, you get this periodicity in the ICs.
> After you pass through transition, however, which typically
> occurs around a time of t ~ 150-200, the ICs are forgotten
> and you should end up w/ a nonperiodic problem.
>
> Paul
>
>
>
> On Tue, 22 Jun 2010, nek5000-users at lists.mcs.anl.gov wrote:
>
>>
>> Hi Neks,
>>
>> I am a newbie and i am trying to learn Nek5000 from the examples.
>>
>> I run the TurbChannel case but i am not convinced by the results.
>> If i plot the x velocity the results look fine but if i plot the y-velocity
>> in an xz plane close to the wall (y=-0.9) the results show clear
>> periodical patterns both in x and z that are believe are not Physical.
>> Moreover these strong periodical structures coincide with the element's
>> boundaries which is suspicious.
>>
>> I have tried to implement previous suggestions on the turbchannel case
>> found on the mailing list( dt=0.025 and simple filtering)
>> but i didn't notice improvements.
>>
>> Do you have any comments/suggestions on this? Do you think i am making a
>> mistake in the plotting or in the settings ( i did a copy and paste of the
>> case in the repository).
>>
>> Thank you for any help
>> francesco
>>
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