velocity profile

rkmittal1108@gmail.com · January 14, 2013, 07:21

Dear friends,
i am trying to plot the velocity profile for a flowing fluid at cross section of open channel using fluent. I have done modelling as well as meshing. Beside these in fluent, i have switched on gravity, in models, i have chosen volume of fluid model>open channel flow, checked energy equation and used k-epsilon (2 eqn.).
I have given water as primary and air as secondary phases. Besides these all are set as default. Still i am not getting the correct velocity profile. please help me. I got stuck since a long time.

rkmittal1108@gmail.com · January 18, 2013, 16:16

Dear friends,
is there no one who is able to help me?

msaeedsadeghi · January 19, 2013, 04:31

It is an easy problem.
Which boundary conditions have you use? There is no need to enable energy equation.

rkmittal1108@gmail.com · January 19, 2013, 05:29

Sir,
boundary conditions are as follows:
(1)At velocity inlet-
v=0 at inlet
initial gauge pressure= 0
turbulence specification method- Intensity and hydraulic diameter
temperature= 300K

(2)At pressure outlet-
back-flow direction specification method- Normal to boundary
turbulence specification method- Intensity and hydraulic diameter
temperature= 300K

checked the open channel in multiphase tab where-
pressure specification method- from neighbouring cell
bottom level i selected which is at outlet side.

(3)Stationary walls-
wall motion- stationary wall
shear condition- no shear
wall roughness- roughness constant= 0.5
roughness height = 0
wall adhesion-
contact angle(air-water)= 90 degree

All remaining conditions are default.

msaeedsadeghi · January 19, 2013, 05:55

in open channels you should use outflow instead of pressure outlet.

rkmittal1108@gmail.com · January 20, 2013, 08:02

As per your saying, i used outflow instead of pressure outlet.
What is flow rate weighting?
Although i took its value equal to one.
But still i am not getting the correct velocity profile.
Sir, if you have already done it before, kindly mail me the way in which i should proceed at rkmittal1108@gmail.com
I will be very thankful to you.

msaeedsadeghi · January 20, 2013, 09:08

Set it 1 if you have just one outlet. Else you should define fraction of flow that gets out of the domain from each outlet.

January 14, 2013, 07:21	velocity profile	#1
rkmittal1108@gmail.com Member Rohit kumar Mittal Join Date: Sep 2012 Posts: 41 Rep Power: 13	Dear friends, i am trying to plot the velocity profile for a flowing fluid at cross section of open channel using fluent. I have done modelling as well as meshing. Beside these in fluent, i have switched on gravity, in models, i have chosen volume of fluid model>open channel flow, checked energy equation and used k-epsilon (2 eqn.). I have given water as primary and air as secondary phases. Besides these all are set as default. Still i am not getting the correct velocity profile. please help me. I got stuck since a long time.

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January 18, 2013, 16:16		#2
rkmittal1108@gmail.com Member Rohit kumar Mittal Join Date: Sep 2012 Posts: 41 Rep Power: 13	Dear friends, is there no one who is able to help me?

January 19, 2013, 04:31		#3
msaeedsadeghi Senior Member SSL Join Date: Oct 2012 Posts: 226 Rep Power: 14	It is an easy problem. Which boundary conditions have you use? There is no need to enable energy equation.

January 19, 2013, 05:29		#4
rkmittal1108@gmail.com Member Rohit kumar Mittal Join Date: Sep 2012 Posts: 41 Rep Power: 13	Sir, boundary conditions are as follows: (1)At velocity inlet- v=0 at inlet initial gauge pressure= 0 turbulence specification method- Intensity and hydraulic diameter temperature= 300K (2)At pressure outlet- back-flow direction specification method- Normal to boundary turbulence specification method- Intensity and hydraulic diameter temperature= 300K checked the open channel in multiphase tab where- pressure specification method- from neighbouring cell bottom level i selected which is at outlet side. (3)Stationary walls- wall motion- stationary wall shear condition- no shear wall roughness- roughness constant= 0.5 roughness height = 0 wall adhesion- contact angle(air-water)= 90 degree All remaining conditions are default.

January 19, 2013, 05:55		#5
msaeedsadeghi Senior Member SSL Join Date: Oct 2012 Posts: 226 Rep Power: 14	in open channels you should use outflow instead of pressure outlet.

January 20, 2013, 08:02		#6
rkmittal1108@gmail.com Member Rohit kumar Mittal Join Date: Sep 2012 Posts: 41 Rep Power: 13	As per your saying, i used outflow instead of pressure outlet. What is flow rate weighting? Although i took its value equal to one. But still i am not getting the correct velocity profile. Sir, if you have already done it before, kindly mail me the way in which i should proceed at rkmittal1108@gmail.com I will be very thankful to you.

January 20, 2013, 09:08		#7
msaeedsadeghi Senior Member SSL Join Date: Oct 2012 Posts: 226 Rep Power: 14	Set it 1 if you have just one outlet. Else you should define fraction of flow that gets out of the domain from each outlet.