|
[Sponsors] |
April 21, 2012, 14:41 |
Scramjet modelling y+ value
|
#1 |
New Member
Stephen
Join Date: Feb 2012
Location: London
Posts: 6
Rep Power: 14 |
Hi, I am modelling a Scramjet intake and think that I have a fine enough mesh however after reading countless documentation about Y+ values I am more confused than ever.
I have an incoming velocity of 2122m/s (Mach 7 at 30,000 feet) along with the corresponding atmospheric conditions. RE = 3.3*10^7 I am modelling this in CFX and have a boundary layer height of 0.0001m. I have calculated this using an assumed value for y+ of 220. The thing is I have no idea if that is acceptable or not. Does anyone have any thoughts? I can always further refine the mesh but don't want to go increase the number of nodes to a ridiculous number for a model that is only 0.5m long. |
|
April 22, 2012, 07:06 |
|
#2 |
New Member
Brad Fowler
Join Date: Feb 2012
Posts: 3
Rep Power: 14 |
If you aren't greatly interested with the boundary layer effects, it could be suitable. What turbulence model are you using? The y+ value depends greatly on what turbulence model you're applying, and what kind of results you're after.
|
|
April 22, 2012, 07:49 |
|
#3 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,700
Rep Power: 143 |
In addition to Brad's comment, the answer to the question "is my mesh fine enough?" is always "Do a sensitivity check and find out". Always better to determine for yourself.
|
|
April 22, 2012, 08:14 |
|
#5 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,700
Rep Power: 143 |
Probably true. But it is best to prove it by doing a sensitivity study, then you will know how big an effect the boundary layer has on the flow. It may even suggest you can coarsen your grid and maintain accuracy (unlikely, but possible).
|
|
April 22, 2012, 09:20 |
|
#6 | ||
Super Moderator
|
Quote:
Quote:
PS. @moonser: Y+ and overall no. of nodes in domain should be studied separately. For such high Mach no. flows the main problem is the resolution of shock waves, so you many need to refine the mesh in the regions of expected shock waves. |
|||
April 23, 2012, 00:12 |
|
#7 |
New Member
唐磊
Join Date: Apr 2012
Location: China
Posts: 8
Rep Power: 0 |
I agree with #2
The y+ value depends greatly on what turbulence model |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
error message | cuteapathy | CFX | 14 | March 20, 2012 06:45 |
A help needed in a scramjet combustion modelling in FLUENT | omar.2002bh | FLUENT | 0 | March 1, 2010 10:27 |
Advice on multi-phase flow modelling | Martin | Main CFD Forum | 3 | October 14, 2008 05:16 |
Unsteady modelling technique? | Carlos | FLUENT | 0 | September 26, 2008 11:37 |
Computational Modelling of Vortex Separators | May Lim | Main CFD Forum | 6 | November 13, 1998 12:36 |