# [Other] How to estimate y+ and set cell division for K-epsilon turbulence model in openFOAM?

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

 December 23, 2014, 22:29 How to estimate y+ and set cell division for K-epsilon turbulence model in openFOAM? #1 Senior Member   Mominul MuKuT Join Date: Mar 2009 Location: Bangladesh Posts: 124 Rep Power: 17 Good morning all! As I told earlier about my simulation in a wind tunnel. I am expecting separation in the diffuser region, to get expected separation proper cell division is necessary. For standard k-e turbulence model I learned from the previous replies that it better to use y+>30. I have found these two sites to calculate y+ http://www.pointwise.com/yplus/ http://www.cfd-online.com/Tools/yplus.php Here is my simulation domain: Straight section height is 200mm which is 630mm long and a diffuser section with 20deg inclination having a length of 250mm. In the above two y+ calculation site, there is a term boundary layer length and reference length, I am confused with these two term because both sites calculates the same but they mention these terms differently. Shall I use this length as 200mm? But in diffuser section these vertical height is a varying height, as it has 20deg slope in bottom wall. BR MuKuT

 December 31, 2014, 16:58 #2 Senior Member   anonymous Join Date: Aug 2014 Posts: 205 Rep Power: 12 Using adimensional parameters is just a way of having a first idea of the magnitude of magnitudes such as yplus. Use the total length of your domain and once you run the simulation use the tool named yPlus in openfoam to know exactly the value of yplus

February 4, 2015, 04:37
#3
Senior Member

Mominul MuKuT
Join Date: Mar 2009
Posts: 124
Rep Power: 17
Quote:
 Originally Posted by ssss Using adimensional parameters is just a way of having a first idea of the magnitude of magnitudes such as yplus. Use the total length of your domain and once you run the simulation use the tool named yPlus in openfoam to know exactly the value of yplus
Thanks a lot. I am using k-omega-SST model instead of K-E now to get more realistic separation as it was found during experiment. In preliminary stage new simulation gives better result than K-E model.

 Tags cell division, mesh and grid, openfoam, yplus

 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 Off Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post amodpanthee CFX 31 April 19, 2018 18:02 alchem OpenFOAM Bugs 5 May 6, 2017 16:30 MStudent FLUENT 1 May 21, 2016 02:31 realpilot FLUENT 2 April 24, 2013 20:26 J.Yang CFX 2 August 29, 2002 15:39

All times are GMT -4. The time now is 16:00.