|
[Sponsors] |
February 8, 2008, 08:14 |
Y star too low
|
#1 |
Guest
Posts: n/a
|
Go a question If my Y star is too low (<30), should I increse the mesh size of the first layer? because FLUENT User Guide says The logarithmic law for mean velocity is known to be valid for 30--300.
(Stander Wall Function, k-e Model) Thanks in advance |
|
February 11, 2008, 03:20 |
Re: Y star too low
|
#2 |
Guest
Posts: n/a
|
Hi!
I only know about y plus value, but i thing, that is almost equal to y star in that region. For your settings, y plus should be between 30 and 300 - so, the answer to your question is YES - increase first layer of your mesh. BUT - as i experienced, k-e, std wall function is not very good (depends of course on the problem). choose sst k-w with a yplus bewenn 1 and 5! Seperation and reattachement can be displayed much more accuratly. Ralf |
|
February 11, 2008, 20:39 |
Re: Y star too low
|
#3 |
Guest
Posts: n/a
|
Deat Ralf Thank you for your answear
I have a case that have a y*=10 in most of the area. but I can not make the first layer mesh bigger because of the geometry. I found this in the FLUENT User Guide "Although FLUENT employs the linear (laminar) law when y*<11.25, using an excessively fine mesh near the walls should be avoided, because the wall functions cease to be valid in the viscous sublayer" Is it means I am also ok with a y*=10? what dose excessively fine mesh mean? how fine is excessive? |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Low Reynolds Number SST Model | Josh | CFX | 41 | June 4, 2023 19:00 |
[Other] StarToFoam error | Kart | OpenFOAM Meshing & Mesh Conversion | 1 | February 4, 2010 04:38 |
Low Pressure, Low Temperature | Luke | CFX | 0 | August 4, 2006 18:36 |
[Commercial meshers] Trimmed cell and embedded refinement mesh conversion issues | michele | OpenFOAM Meshing & Mesh Conversion | 2 | July 15, 2005 04:15 |
Multicomponent fluid | Andrea | CFX | 2 | October 11, 2004 05:12 |