# flow depth in 2D open channel ?

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

 November 20, 2007, 13:18 flow depth in 2D open channel ? #1 rodi Guest   Posts: n/a Hi ! I am working in a 2D open channel with VOF,two phase:air /water.The flow depth at the inlet is specialed ,and I get the free surface ,but how to compute the flow depth at outlet? Just multiply Area by volume fraction of water? Thanks! rodi

 November 20, 2007, 13:56 Re: flow depth in 2D open channel ? #2 bohis Guest   Posts: n/a Hi, you donīt need to set the depth of water at a outlet. You should only patch the domain according to the physics and adjust the correct backflow at the outlet. Enjoy your calculation bye, Jan

 November 21, 2007, 04:42 Re: flow depth in 2D open channel ? #3 rodi Guest   Posts: n/a Thank you! Maybe i can express my question much clearly~ When the caculation has done,and i got the free surface.During the postprocessing,I want to know the water level at the outlet,what can i do? For 2D simulation,the channel is rectangle. Can i just multiple the water phase fraction by the area of outlet? Thanks! rodi

 November 21, 2007, 12:34 Re: flow depth in 2D open channel ? #4 k.baker Guest   Posts: n/a dear rodi you can find the height of water at the outlet from the value of vof at outlet directly by trial and error from the following relation: RL=(1/pi)*(pi-acos(2*(hL/d)-1)+(2*(hL/d)*SQRT(1-(2*(hL/d)^2)) where RL is the vof of liquid (water) & hL is liquid height I hope this fullfill your request another thing I sent you two emails envolve some questions about your case file which you sent me did you see it or no? did you see my case & data file too? hope to see your reply soon cheers kb

 November 22, 2007, 01:04 Re: flow depth in 2D open channel ? #5 sushii Guest   Posts: n/a What is Backflow....and how dose it affects the calculations...? Sometimes when simulating I set backflow volume fraction and backflow turbulent KE....to zero...does it affect the solution...? if yes then how to calculate right backflow volume fraction and turbulent KE...? ---Sushii..

December 2, 2010, 01:02
Open Channel Flow boundary conditions
#6
New Member

Join Date: Mar 2010
Posts: 14
Rep Power: 9
Quote:
 Originally Posted by rodi ;146875 Thank you! Maybe i can express my question much clearly~ When the caculation has done,and i got the free surface.During the postprocessing,I want to know the water level at the outlet,what can i do? For 2D simulation,the channel is rectangle. Can i just multiple the water phase fraction by the area of outlet? Thanks! rodi
HI,
I am Rahul. I am also working on Open Channel Flow in Fluent solver. I used
Mass Flow Inlet bc
mass flow of air is 7985.6 kg/s, free surface of water is at 2m, bottom at 0m,
Pressure Outlet bc

In my case the, the channel is rectangular of cross section 4mx3m. Out of 3m height upto 2m there is water. Now I really dont understand what boundary condition should I use for remaining 1m. The geometry is attached herewith.

One more thing to be discussed is that, should I patched volume fraction of water( secondary phase) initially through out the domain. I am trying for steady state simulation.

If somebody have a test case for open channel flow pls do send me on praghanmor@gmail.com

Hoping for ur fruitful suggestions.
Thanks.
Attached Images
 nomenclature_geometry.jpg (21.7 KB, 16 views)

 January 25, 2011, 11:03 #7 New Member   Join Date: Feb 2010 Posts: 4 Rep Power: 9 Hi rahulrp what does your mesh look like? darp

 January 26, 2011, 00:03 #8 New Member   anonymous Join Date: Jan 2011 Posts: 23 Rep Power: 8 Hi, I you take mass flow inlet boundary for open channel, then both water and air can enter from the same. Specify free surface level Specify bottom level Specify mass flow rate of water as = rho_water *Area_water*Velocity Specify mass flow rate of air as = rho_air* Area_Air * Velocity You can use the same velocity for both water and air.

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Andy CFX 9 June 11, 2016 07:20 ElanMorin FLUENT 4 February 25, 2015 17:26 ms.jafarinik FLUENT 0 April 18, 2010 14:38 khalid FLUENT 1 November 4, 2006 12:53 ao Main CFD Forum 0 April 6, 2004 16:21

All times are GMT -4. The time now is 00:24.