Hi,

Not sure if anyone responded to this request. Regarding your points

1) I presume you are using 2.5D (Fourier modes in the third direction). Certainly you should use spectralhp dealiasing and probably the most efficient is to use SVV in the Fourier direction at least. We have tried to set the default parameters to be of some help but they are not perfect. Ultimately if you are resolved enough then it will be fine but before then you will likely need some stabilisation.

2) Not really sure about this. The non-linear nature of the process makes that challenging to answer. 

3) I think we do have filters that are of use. There is a FilterReynolsStresses in the directory

Nektarpp/solvers/IncNavierStokesSolver/Filters

Sorry I did not write this but there seem to be a bit of documentation in the user-guide.

Cheers,
Spencer.


On 4 Feb 2021, at 23:43, DEBSHANKAR GHOSH <f2016559p@alumni.bits-pilani.ac.in> wrote:

Hi,

I have been trying to simulate the Turbulent Channel flow test case as well using the same session file. What I found was transition takes a bit of time to kick in, so it's better to use a higher time step and keep storing files every 5-10 time units, as has been suggested in a previous thread. I do have a few doubts queries I would like to post to the community though:

1. The turbulent flow that results from my simulations is pretty unstable and keeps diverging frequently. I have used "DEALISING" to stabilize the flow, but it's not much help. I understand that I can use SVV parameters to stabilize the flow, but is there any workaround for this? Also, how do I know what SVV parameters to use?
2. Can I use a higher noise value to kickstart the transition process faster?
3.Are there any filters I can use to calculate the turbulent kinetic energy budgets?

Regards,
Debshankar Ghosh
Graduate Student
Faculty of Applied Science | School of Engineering
The University of British Columbia | Okanagan Campus
EME 1240 3333 University Way | Kelowna British Columbia | V1V 1V7 Canada


On Thu, Feb 4, 2021 at 8:50 PM Eli Frydman <elimanu123@gmail.com> wrote:
This email from elimanu123@gmail.com originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list to disable email stamping for this address.
 
Hi all,

I tried to run the turbulent channel flow test case from the user guide (session file TurbChFl_3DH1D.xml) but i didn't get any turbulent flow. I used a body force in the u direction as explained and added also a perturbation in the spanwise direction and didn't get any transition.

Regards, 
Eli
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