CFD Online Logo CFD Online URL
Home > Forums > CFX

free surface flow simulation to a junction flows

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

LinkBack Thread Tools Display Modes
Old   September 21, 2011, 17:35
Default free surface flow simulation to a junction flows
New Member
emily chen
Join Date: Mar 2011
Posts: 3
Rep Power: 8
emily_cx is on a distinguished road
hi everyone, I am doing a free surface modelling of two flows junction. I have some experimental data to validate the model. However, the numerical results are not as good as expected which don't have a good agreement with my lab data. So here I want to ask some of you to give me some advice to help me out.

Domain description: a main channel with 20m long and 1m wide orthogonally intersected by a branch channel at around 5m distance from the main channel's upstream. The branch channel is about 8m long and has the same width with main 1m.
Modelling description: Most of the settings are based on the Tutorial. But in this case I have two inlets, the expressions for the brach channle inlet are created the same as the main channle inlet (I am not sure this setting is right or wrong), the model is run as steady state (I read some previous comments on free surface, some people said always run transient for free surface, so would it be a source of error? but I got converged for steady state). The inlet boudary conditon is set to be mass flow rate, the outlet b.c. is static pressure with a constant water height (I know the exact tail water height), and the top of the channel is set to be openning with zero pressure gradient

Any other things I should consider for the simulation? Although I got every target achived, I really have no idea what's the problem for the non-accuracy. Can anybody give me some suggestions what I should do next?

Thank you very much!
emily_cx is offline   Reply With Quote

Old   September 21, 2011, 19:19
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 14,094
Rep Power: 109
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
It is unusual for free surface simulations to converge in steady state - it suggests to me that you may have excessive dissipation in your model. Are you using high resolution differencing?

You would have to explain what the poor agreement with experiment is for us to help you further.
ghorrocks is online now   Reply With Quote


Thread Tools
Display Modes

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 Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Free surface flow settubg boundary conditions and plotting velocity profiles prashanthreddyh FLUENT 2 October 21, 2015 09:58
Free surface vortex flow Guillaume CFX 3 August 25, 2005 20:52
viscous free surface flow past a ship hull lololo Main CFD Forum 0 June 12, 2002 23:02
fluid flow fundas ram Main CFD Forum 5 June 17, 2000 21:31
Modeling Free Surface Flows Elliot Schwartz Main CFD Forum 5 August 25, 1998 21:03

All times are GMT -4. The time now is 07:30.