|
[Sponsors] |
July 13, 2006, 06:36 |
Asymmetric Flow
|
#1 |
Guest
Posts: n/a
|
Hi,
I am simulating the compressible internal flow within a curved duct using a RANS-based flow solver. The duct is symmetric wrt the center plane. The solution that I get is rather surprising as the flow after the mid longitudinal station loses its symmetric nature and becomes totally asymmetric downstream the duct. If you have any idea what really cuases this, please help me out here. I really do not have any answer for that. It cannot be correct I think, so there muct be something wrong in my flow calculations. Thank you. Rose |
|
July 13, 2006, 07:04 |
Re: Asymmetric Flow
|
#2 |
Guest
Posts: n/a
|
Just to mention that when I said "there muct be something wrong in my flow calculations", I should have said that the code I am using is very robust and has been used in the lab for many years, it works very well for many applications, and my case is actually very close to those applications, I just do not understand why the solution looks unreasonable.
Rose |
|
July 13, 2006, 16:02 |
Re: Asymmetric Flow
|
#3 |
Guest
Posts: n/a
|
Are your calculations 2D or 3D? How do your profiles look? Like symmetric profiles that are biased to one side? What kind of RANS Model do you use? Does it have some handling for rotational effects? Asymmetries can occur because of system rotation
|
|
July 14, 2006, 08:54 |
Re: Asymmetric Flow
|
#4 |
Guest
Posts: n/a
|
My calculations are 3D. The symmetric pattern starts being disappeared from the middle of the duct. If you look at the cross-sections at tdifferent longitudinal locations, the bottom separated region circumferentially moves towards the right side and by the very downstream, it even reaches to the top of the duct; ie, a full 180-degree rotation. The core of the flow however is not affected that much.
The RANS model of the code is: 0-, 1- and 2-equation, although for my first cases, 0-equation model seemed to produce more accurate solutions, so I am now more stick to this model than 1- or 2-eqs, it is also much faster. System rotation should not be a problem here because if it was, this asymmetric pattern should have started from the duct entry, not from the mid-way. Any advice? Rose |
|
July 17, 2006, 08:33 |
Re: Asymmetric Flow
|
#5 |
Guest
Posts: n/a
|
Hi,
Such asymmetry can be physical if there is a symmetry-breaking bifurcation of the flow resulting in multiple stable solutions. The only constraint is that the ensemble-average of the realizable flows has to be symmetrical. Do your computations always result in the same asymmetric pattern or sometime in a mirror-reversed image (you could try to change the initial solution, possibly to an asymmetric one to check it)? Moreover, from my experience, such bifurcation are generally related with separation: is your duct curved enough to result in some reverse flow? Hope this helps, Lionel |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
benchmark: flow over a circular cylinder | goodegg | Main CFD Forum | 12 | January 22, 2013 11:47 |
Mass flow and U-Mom flow in CFX | Zhihua Xie | CFX | 0 | September 3, 2007 09:49 |
reversed flow at velocity inlet / mass flow inlet | ib | FLUENT | 1 | March 26, 2007 13:11 |
How to change from mass flow to volume flow rate | stanley | FLUENT | 1 | February 2, 2007 06:44 |
transform navier-stokes eq. to euler-eq. | pxyz | Main CFD Forum | 37 | July 7, 2006 08:42 |