where is Reference Level

flow_CH · June 5, 2013, 10:18

Hello.
I want to model a free surface channel.
i am using "Open channel flow" option in fluent but when i am starting the solver and its done there is no any fluid into the model (there is just air).
my question is: where is the reference level in defining pressure inlet and pressure outlet of channel. please see attached images
thanks

oj.bulmer · June 5, 2013, 10:51

Probably you haven't patched the volume fractions of water and air properly. Have a look at the VOF tutorail in FLUENT

OJ

flow_CH · June 5, 2013, 11:11

Quote:

Originally Posted by oj.bulmer

Probably you haven't patched the volume fractions of water and air properly. Have a look at the VOF tutorail in FLUENT

OJ

thanks for your reply.
i read all fluent user guide but i don't understand what the patch is? what parameters i should define in patch for open channel flows.
I think my problem is in reference level.

oj.bulmer · June 6, 2013, 06:44

You need to mark the registers where the fluid exists, and during initialization, set the value for volume fraction for the registers as 1. It's only then that you will have two fluids with volume fractions 1 in different regions, separated by the interface.

OJ

flow_CH · June 6, 2013, 09:29

i know that. my question is: where is reference level in defining free surface and bottom of channel in OPEN CHANNEL FLOW option.

oj.bulmer · June 6, 2013, 10:58

Well the reference level should be any arbitrary point, probably determined by the origin of your geometry. Just make sure that you give appropriate signs of the levels such that:
"free surface level" - "bottom level" = height of open channel flow

Does this help?

OJ

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June 5, 2013, 10:51		#2
oj.bulmer Senior Member OJ Join Date: Apr 2012 Location: United Kindom Posts: 473 Rep Power: 20	Probably you haven't patched the volume fractions of water and air properly. Have a look at the VOF tutorail in FLUENT OJ

June 6, 2013, 06:44		#4
oj.bulmer Senior Member OJ Join Date: Apr 2012 Location: United Kindom Posts: 473 Rep Power: 20	You need to mark the registers where the fluid exists, and during initialization, set the value for volume fraction for the registers as 1. It's only then that you will have two fluids with volume fractions 1 in different regions, separated by the interface. OJ

June 6, 2013, 09:29		#5
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	i know that. my question is: where is reference level in defining free surface and bottom of channel in OPEN CHANNEL FLOW option.

June 6, 2013, 10:58		#6
oj.bulmer Senior Member OJ Join Date: Apr 2012 Location: United Kindom Posts: 473 Rep Power: 20	Well the reference level should be any arbitrary point, probably determined by the origin of your geometry. Just make sure that you give appropriate signs of the levels such that: "free surface level" - "bottom level" = height of open channel flow Does this help? OJ