Divergence with Simulation using Embedded LES

CarlosGRR · October 1, 2014, 20:24

Hello All,

I have problems of divergence whit my simulation in Fluent. My case is about a High Lift Configuration (see http://hiliftpw.larc.nasa.gov/). I am using Embedded LES for this simulation, with SST k-omega for the URANS part, and Smagorinsky-Lily for the LES part. For the interface RANS to LES I am using the Vortex method.

I've checked the Boundary conditions and these are good for my case, but in te calculation, the simulation diverges in the first iteration. What can i do to get rid of that problem? Any suggestions?

Regards,

Carlos Ramirez

hwet · October 2, 2014, 11:13

There can be dozens of reasons for divergence, post you geometry and mesh maybe to start with, also although i am no expert but LES should not really be used for simulations, there are too many complexities associated with it and for general flows rans based model would suffice. leave the LES for NASA.

sbaffini · October 2, 2014, 15:14

While i do not agree with the previous poster on not doing LES, i agree that you should maybe first try RANS/U-RANS on the same grid and see what happens. Then switch to LES

CarlosGRR · October 2, 2014, 18:52

Thanks for your reposts. I tried run the simulation only with the URANS and the simulation diverges too. I think that the divergence in my case is in the problem itself, that it's complex. My case have a grid with 12'700.000 elements.

October 1, 2014, 20:24	Divergence with Simulation using Embedded LES	#1
CarlosGRR New Member Carlos G. Ramirez R. Join Date: Oct 2014 Posts: 3 Rep Power: 12	Hello All, I have problems of divergence whit my simulation in Fluent. My case is about a High Lift Configuration (see http://hiliftpw.larc.nasa.gov/). I am using Embedded LES for this simulation, with SST k-omega for the URANS part, and Smagorinsky-Lily for the LES part. For the interface RANS to LES I am using the Vortex method. I've checked the Boundary conditions and these are good for my case, but in te calculation, the simulation diverges in the first iteration. What can i do to get rid of that problem? Any suggestions? Regards, Carlos Ramirez

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October 2, 2014, 11:13		#2
hwet Senior Member Join Date: Mar 2014 Posts: 375 Rep Power: 13	There can be dozens of reasons for divergence, post you geometry and mesh maybe to start with, also although i am no expert but LES should not really be used for simulations, there are too many complexities associated with it and for general flows rans based model would suffice. leave the LES for NASA.

October 2, 2014, 15:14		#3
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,195 Blog Entries: 29 Rep Power: 39	While i do not agree with the previous poster on not doing LES, i agree that you should maybe first try RANS/U-RANS on the same grid and see what happens. Then switch to LES

October 2, 2014, 18:52		#4
CarlosGRR New Member Carlos G. Ramirez R. Join Date: Oct 2014 Posts: 3 Rep Power: 12	Thanks for your reposts. I tried run the simulation only with the URANS and the simulation diverges too. I think that the divergence in my case is in the problem itself, that it's complex. My case have a grid with 12'700.000 elements.