[Nek5000-users] DNS of turbChannel

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

Dear Emily,


Attached is a channel flow example with a 90-element mesh generated

by genbox.   It has 6 elements in the wall-normal direction, which for polynomial

order N=7 (lx1=8 in the SIZE file) implies 42 points in the wall normal direction.

I have run this case with lx1=12 (implying 6x11 = 66 points in the wall normal

direction) as a reasonable LES for Re_tau=395.


You can reach a DNS solution with increased resolution by increasing the polynomial order or by refining the mesh through changes to the box file and rerunning genbox and genmap.


The .usr file should be fine in this case - it has no eddy-diffusivity.   The .rea file does prescribe a filter here:   param 103 = 0.05 and p101=1 implies 5% of the energy is removed from the Nth mode in the velocity field at each time step and 5% x (1/4) of the energy in the (N-1)th mode at each step.   In the limit that you approach DNS, the amount of energy in these modes is in any case small, so you don't need to worry about turning them off, but you could do so if you wanted.


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: Thursday, February 8, 2018 3:37:41 PM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] DNS of turbChannel


Dear Nek users,



I am new to NEK5000. I am aware of that two SGS models are available for the turbChannel. But if I am looking for a DNS, which line/subroutine shall I deactivate?



Thanks a lot for the help.



Regards,



Emily
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