# LES turbulence decaying in channel flow

 Register Blogs Members List Search Today's Posts Mark Forums Read

 July 3, 2008, 17:08 LES turbulence decaying in channel flow #1 cfdIsMad Guest   Posts: n/a Hi I am running a channel flow using LES. My problem is that turbulence after developing for a bit starts to decay in channel. And after a while I see zero turbulence in my domain. What can I do under such circumstances to sustain the turbulence. Thank you for your answer.

 July 3, 2008, 18:25 Re: LES turbulence decaying in channel flow #2 Glenn Horrocks Guest   Posts: n/a Hi, Accurate LES modelling is not easy, I hope you are not a CFD beginner. If you have not heard of the -5/3 line or never drawn a turbulence spectrum then I suggest you do some study of turbulence theory before proceeding. A major problem in LES modelling is dissipative advection schemes causing energy to lost numerically before it trickles down the subgrid model. To counter this most LES models use central differencing as it does not have the numerical dissipation of the default upwinding schemes. Glenn Horrocks

 July 3, 2008, 18:35 Re: LES turbulence decaying in channel flow #3 cfdIsMad Guest   Posts: n/a Hi Glenn CFX is using central difference scheme, yet it cant sustain the turbulence. I know how to draw energy spectrum and I understand the basic physics of LES. I will be thankful if you can give any hints/suggestions to model plane channel flow so that I can sustain turbulence and get fully developed flow. I am using periodic boundaries and I have set pressure drop between inlet and outlet. Do I need to set up pressure gradient as well under subdomain??? Thanks in advance

 July 3, 2008, 22:17 Re: LES turbulence decaying in channel flow #4 Glenn Horrocks Guest   Posts: n/a Hi, You are using translational periodic boundaries with a pressure drop? That should be sufficient, the flow rate should then adjust so the pressure drop in the domain equals the pressure rise is the periodicity. No need to define a subdomain. Glenn

 July 4, 2008, 06:29 Re: LES turbulence decaying in channel flow #5 cfdIsMad Guest   Posts: n/a Hi Glenn Yes, I am using translatinal periodic boundary with the pressure drop. Thank you for you answer.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post eelcovv OpenFOAM 0 June 8, 2010 11:35 gRomK13 Main CFD Forum 1 July 10, 2009 03:11 Wen Long Main CFD Forum 3 May 15, 2009 09:52 Hadi FLUENT 0 September 20, 2007 05:15 ram Main CFD Forum 5 June 17, 2000 21:31

All times are GMT -4. The time now is 03:22.