[Nek5000-users] Tripping mechanism
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Fri Feb 23 15:49:37 CST 2018
Hi Juan Diego,
Indeed, we describe in our paper the trip forcing. The tripping has a
temporal part (third-order Lagrange interpolants with specific time
scale) and a spatial part (the h^i(z)). We typically use white noise for
these h(z), low-pass filtered with a spectral cutoff filter at a
wavenumber 2pi/z_s. So what one gets in h(z) is just random sines and
cosines up to a spanwise scale z_s.
The implementation of course needs to make sure i) that you have the
same random numbers for the whole spanwise extent, and ii) that when
restarting a simulation you continue the previous tripping in a smooth
way as to not generate any peaks (discontinuities) at the restart.
Please let me know if you have further questions, and I am happy to help
more.
Best regards,
Philipp Schlatter
On 2018-02-23 18:29, nek5000-users at lists.mcs.anl.gov wrote:
> Dear all,
>
>
> I've seen several papers using Nek5000 with a tripping mechanism based
> on a forcing term, explained in a paper by Schlatter & Örlü (2012).
> However, they talk about using random harmonic signals h^{i}(z). My
> question is: What is the shape of such signals and how do you make them
> random?
>
>
> Thanks,
>
>
> Juan Diego
>
>
>
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