|
[Sponsors] |
July 11, 2005, 11:56 |
roughness and y+ constraints
|
#1 |
Guest
Posts: n/a
|
Hi,
I am modeling an atmospheric boundary layer flow and I have a wall roughness of 1.6m I have a 2D domain of 1000m height. I meshed with a cell height of 4m, but I still have a viscosity ratio problem and my y+ is around 10000. If I refine my mesh to get smaller y+ going down to a cell height of 2m near the wall, my roughness height will exceed the center of my cell adjacent to the wall. I am using wall function k-epsilon. Please help Thank you |
|
July 12, 2005, 09:54 |
Re: roughness and y+ constraints
|
#2 |
Guest
Posts: n/a
|
Change your turbulence model to SST-kw. If this does not solve the problem, change some settings for multigrid:
- set presweeps=postsweeps=2 - set pressure and all momentum to F-cycle - set turbulence quantities to V-cycle If this will not solve the problem, then I do not know what else you can do. Hope this will help you. Best wishes, Razvan |
|
July 12, 2005, 13:35 |
Re: roughness and y+ constraints
|
#3 |
Guest
Posts: n/a
|
Thx Razwan,
I am modeling wind turbine effect on the atmospheric layer. Is the k-w convenient for such a problem? The domain is rectangular. I chose a velocity inlet, an outflow and a symmetry boundary for the top of the domain at 1km height. Do you think those boundaries are convenient? Thank you |
|
July 14, 2005, 03:44 |
Re: roughness and y+ constraints
|
#4 |
Guest
Posts: n/a
|
Not k-w but SST-kw. You should better change the "outflow" boundary to "pressure-outlet" with outlet pressure value=local(desired) atmospheric pressure. If you are modeling wind turbine then I think 1km might be too much. I am not experienced in this tipe of situation, but I don't see no problem in lowering it to say, 150-200m top. That should be enough. Of course, if you are interested in high winds also, this could be an explanaition for a such big domain you have chosen.
Best wishes, Razvan |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
nutRoughWallFunction and Surface Roughness Documented | AlanR | OpenFOAM Programming & Development | 64 | January 6, 2024 07:13 |
Laminar flow and wall roughness | junbbung | FLUENT | 2 | November 26, 2022 21:22 |
Surface roughness in Flow-3d | Marco | FLOW-3D | 3 | June 3, 2018 02:15 |
NACA standart roughness | DAK565656 | Main CFD Forum | 2 | August 24, 2005 00:47 |
Roughness adaptation in CFX 4.4 | Bart | CFX | 1 | May 2, 2003 08:32 |