CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

Fluent Vortex Method Turbulence/General NRBC Compatibility

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 30, 2021, 18:57
Default Fluent Vortex Method Turbulence/General NRBC Compatibility
  #1
New Member
 
Josh
Join Date: Apr 2021
Posts: 1
Rep Power: 0
PhoenixCFD is on a distinguished road
I'm working on an LES model (pressure-based, coupled solver, WALE) of a rather small premixed methane-air burner with a ~1" diameter intake system. It uses a velocity inlet with a defined velocity profile and vortex method turbulence generation with defined Reynolds stress distributions. The setup works very well and is in excellent agreement with PIV data. The problem arises when I try to apply the general non-reflecting boundary condition (NRBC) to the inlet. When I do, the synthetic turbulence "freezes" and all of the turbulent fluctuations at the inlet maintain their last value.

There are three relaxation terms in the documentation in reference to the general NRBC (sigma, sigma2, relax). The "sigma2" term has a default value of 5 and applies only to density-based solvers and the "relax" term has a default value of 0.5 and affects overall convergence. The "sigma" term has a default of 0.15 and is only explicitly described under the pressure outlet section where it is used to calculate the relaxation factor. This "sigma" is the relaxation factor I expected tune; however, I can't seem to find a value that works. There is also one additional option for "tangential-source?" (yes or no) in the TUI that doesn't show up anywhere in the documentation aside from an unrelated "fan" model. It isn't even included in the list of TUI commands in the documentation under "general-nrbc." I haven't been able to determine exactly what it does. These appear to be all the "levers" I have access to regarding the NRBC.

Aside from impacting the synthetic turbulence, the NRBC does function and incoming waves pass through the boundary as expected. I am simply unable to get the NRBC to function without affecting the synthetic turbulence generation. If anyone here has experience with this I'd appreciate your suggestions. Let me know if you need additional details regarding the model. Thanks in advance!

Last edited by PhoenixCFD; April 30, 2021 at 20:59.
PhoenixCFD is offline   Reply With Quote

Reply

Tags
nrbc, velocity inlet, vortex method


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 Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Cleaner method to Fluent Journals/Scheme MN FLUENT 1 November 7, 2017 03:38
Vortex Tube Mesh and Simulation in Fluent sankeerth2292 FLUENT 2 March 13, 2015 23:52
Ghost Fluid Method in Fluent ndabir FLUENT 0 February 3, 2015 09:44
Vortex generators using fluent Hardeep FLUENT 1 July 22, 2013 07:16
problem in using parallel process in fluent 14 aydinkabir88 FLUENT 1 July 10, 2013 03:00


All times are GMT -4. The time now is 23:52.