[Nek5000-users] problem with turbCahnnel case

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

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
>