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co2 December 4, 2003 23:05

flow in pipe
I have a simple pipe flow and I am trying to get the fully developed profile for both velocity and temperature. Hence I have modeled it to be long about 50 times the diameter. But I am not sure what inlet and outlet BC combinations I should be using.

Do I use Velocity inlet + pressure-outlet?


Mass-flow inlet + pressure-outlet?

Please let me know

ccc December 5, 2003 04:29

Re: flow in pipe
hi co2,

How about the compressibility of the fluid in your case? In general, velocity inlet is adopted for incompressible one and mass-flow for compressible one, especially ideal gas.

good luck.

co2 December 5, 2003 11:54

Re: flow in pipe
I dont worry about the variation in rho. it is water. so I guess vel inlet is taken care of. what about the outlet? it is pressure outlet or outflow?

ap December 5, 2003 13:18

Re: flow in pipe
Velocity inlet is the appropriate BC for your case (incompressible fluid).

For the outlet, if you know the pressure at the outlet, use a pressure-outlet BC. If you don't know it, switch to Outflow BC.

You want to model a fully developed flow, so Outflow can be a good choice.

Hi :)


ccc December 6, 2003 11:22

Re: flow in pipe
hi co2,

I agree with ap.

good luck.

chandra December 21, 2003 19:39

Re: flow in pipe
i think no neccesary to doubt vel inlet or mass inlet, it depend to the fluid properties, it is not the must to make vel in let for incompressible,

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