CFD Online Logo CFD Online URL
Home > Forums > FLUENT

Y+ Values for a sperating flow over a hill

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

LinkBack Thread Tools Display Modes
Old   July 7, 2005, 09:49
Default Y+ Values for a sperating flow over a hill
Posts: n/a
Hey, I'm somewhat new to the whole CFD thing and though im learning quickly i've got to a part that has stumped me! see i have this 2d model where there is a small hill that wil produce a seperation in flow. I've opted to use a k-e viscous model as thats what dassault aviation used for a similar model. And according to the userguide an RNG would give better results! anyway.. i've been told that i want a y+ value of between 30 and 300 so that it follows the law of the wall. The problem i find is that when you get to the parts where it seperates the y+ values just dip to values around 0 -5 depending on the grid. The only grid that i've managed to get higher that 30 values for y+ is one that is rather large relative to the model. hence im loosing accuracy due to the large boundary layer mesh! people have said i want a fine B.L mesh though all that i've tried give me really small y+. Its realy stumped me! any suggestions? would the low y+ values at the speration points really effect the result so much?
  Reply With Quote

Old   July 8, 2005, 00:16
Default Re: Y+ Values for a sperating flow over a hill
Posts: n/a
well if you have yplus near to 3 (manual say 1 would be better), what you can do is use enhanced wall treatment for it. where it needs the mesh in the yplus you are talking about.
  Reply With Quote

Old   July 9, 2005, 23:18
Default Re: Y+ Values for a sperating flow over a hill
Posts: n/a
1) Use enhanced wall treatment as Zxaar mentioned. For this will need a finer mesh.

2) Adapt the grid that you are already using for Y+ so that you Y+ lies between say 30-60. Then use non-equilibrium wall funtions.

  Reply With Quote


Thread Tools
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 On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Compressible flow, no data at the outlet mireis FLUENT 6 September 3, 2015 02:10
flow over a cylinder urgent! kevin FLUENT 8 August 11, 2015 13:00
low rms values in pipe flow mehrdad_kbg ANSYS 0 September 8, 2010 11:45
Mass flow and U-Mom flow in CFX Zhihua Xie CFX 0 September 3, 2007 09:49
transform navier-stokes eq. to euler-eq. pxyz Main CFD Forum 37 July 7, 2006 08:42

All times are GMT -4. The time now is 12:02.