Hi both, You certainly need some noise or other Fourier-direction perturbation to excite the other modes, otherwise the flow is confined to the mean mode and won't be able to transition. It looks like for whatever reason this isn't included in the session file, so wouldn't therefore expect transition without it. You might try changing the initial condition on the u/v/w fields to include a source of noise: <E VAR="u" VALUE="1 + 0.0001*awgn(1.0)" /> <E VAR="v" VALUE="0.0001*awgn(1.0)" /> <E VAR="w" VALUE="0.0001*awgn(1.0)" /> The channel transition can be rather abrupt and can blow up pretty easily. The timestep may therefore need adjustment around transition to avoid this, so I suggest you store checkpoint files at semi-regular intervals so that you can backtrack. I also highly recommend the use of the ModalEnergy filter -- this outputs the energy of the Fourier spectrum and is very useful in seeing what's going on in the high frequency modes as a function of time. Cheers, Dave
On 2 May 2016, at 23:36, Sherwin, Spencer J <s.sherwin@imperial.ac.uk> wrote:
Hi Cesar,
Sorry I have not looked at this case for quite some time. i had forgotten it was described in the user-guide.
I think the issue is that really one needs some random noise to kick these flows. It does not look like there is one in this case. I will have a chat with Douglas to see if he has run this case recently so we can confirm how best to get thing going.
Cheers, Spencer.
On 29 Apr 2016, at 08:34, César Alegre <eaxca1@nottingham.ac.uk> wrote:
Dear all,
I have recently downloaded Nektar++ 4.3.0 and started doing the examples as shown in the user guide for the incompressible Navier-Stokes solver.
I am having some problems trying to reproduce the results of the "Turbulent Channel Flow" (TurbChFl_3DH1D.xml). The simulation runs without issues, but after converting the final .fld file to .vtu for visualization in Paraview, I still see a velocity field equal to that of the initial condition (u = 1 everywhere except near the wall), instead of the expected turbulent flow.
Has anyone experienced a similar outcome? Maybe I have to change something (simulation time?) in the .xml file before running the solver?
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