CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

very strange velocity profiles for kOmegaSST model (with or with out wall function)

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

LinkBack Thread Tools Search this Thread Display Modes
Old   February 26, 2022, 07:09
Default very strange velocity profiles for kOmegaSST model (with or with out wall function)
Senior Member
Join Date: Jun 2020
Posts: 100
Rep Power: 5
atul1018 is on a distinguished road
Hello Community

Let me explain what I want to do: I want to simulate particle-infiltration phenomena in Flume. I am using CFDEM coupling (OpenFOAM+Liggghts) for this purpose. Firstly, I perform pure DEM simulation where I fill large particle in a cavity section within the channel and then let the small particles gets injected with water from inlet of channel (here both CFD and DEM are active). As per experiment I am simulating, the bed remians stable (large particles in cavity doesn't get transported) and only small particles get transported and infiltrated in the bed (i.e cavity). The flow is turbulent therefore flow needs to be reresolved using turbulence modeling.

As flow is turbulent, I want the flow at the inlet of channel as fully developed turbulent flow and for the same purpose I am using mapped bc. By mapping flow fields from a cetrtain offset from inlet back to inlet I should get fully developed turbulent flow. In the third dimension (front and back plane) I am using symmetry bc. top and bottom channel is treated as no slip walls. The initial turbulence parameters are estimated as per guidelines provided here in CFDEM wiki by assuming turbulence intensity of 4%. The estimated YPlus is around 100-200. I tried both kEpsilon and KOmegaSST with and without wallfuncitions and found out only KEpsilon (without wall functions) produces velocity profiles similar to fully develped channel flow (peak at the centre of channel). When wall functions are used with KEpsilon the peak get shifted near to upper wall. Similar observations are also found in KOmegaSST (with or without wall functions) where is is observed either near to upperwall or lower wall but not at the center. I wonder why KOmegaSST performs in this stange way?

As I am having higher Yplus values I must use wall functions (in both case KEpsilon and KOmegaSST) but even with wallfunctions results are very strange and incorrect velocity profiles (peak near tro walls) is observed. What could be the reason for this?

Looking farward to hear from seniors.

Best Regards
Atul Jaiswal
atul1018 is offline   Reply With Quote

Old   April 5, 2022, 08:10
Julio Pieri
Join Date: Sep 2017
Posts: 96
Rep Power: 8
JulioPieri is on a distinguished road
Dear Atul,

Sorry for the delay. By now, you might already have solved your problem.
Have you tried changing your mesh resolution a bit? One possibility is that you are in the exact transition yPlus value so that your first cell keeps changing from viscous sublayer to outer layer.

Do a mesh sensibility study on a simpler case. Get the channel with same properties and try simulating your problem with different near-wall mesh resolution (thus yPlus). Check the different possibilities (enhanced wall treatment, different laws, etc), without randomly changing it to see if the results are as expected. Study the different wall treatment options and see which one suits your problem.
JulioPieri is offline   Reply With Quote


cfdem, fully developed flow, kepsilon, komegasst, wallfucntion

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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
Ansys CFD-Post Application Error rushiCFD FLUENT 0 March 21, 2021 07:51
Table bounds warnings at: END OF TIME STEP CFXer CFX 4 July 16, 2020 23:44
Radiation in semi-transparent media with surface-to-surface model? mpeppels CFX 11 August 22, 2019 07:30
Question about adaptive timestepping Guille1811 CFX 25 November 12, 2017 17:38
A girl fail to plot velocity profile when mesh changes + Wall function asherah STAR-CCM+ 0 February 19, 2010 17:45

All times are GMT -4. The time now is 08:12.