inlet velocity in free surface in CFX

yaseen wsu · March 30, 2016, 04:52

CFX is sensitive to velocity inlet in free surface flow in transient simulation,
I dont know accurately velocity so, instead velocity what I should entered, in intial condition and velocity inlet (note: I know flow rate in m3/sec)

ghorrocks · March 30, 2016, 08:01

The whole point of a boundary condition is that you know the conditions at that location so you don't need to model it, you can specify it and it becomes the boundary of the modelled region. If you cannot specify the flow conditions then you cannot put a boundary condition there.

If you know the volume flow but you do not know the free surface level then consider a boundary where the flow wells up from below into a chamber connected to your domain. You can define the inlet pipe to have pure water at your flow rate, and it will determine the free surface level itself.

March 30, 2016, 04:52	inlet velocity in free surface in CFX	#1
yaseen wsu Senior Member yaseen Join Date: Oct 2015 Location: Hawler Posts: 174 Rep Power: 11	CFX is sensitive to velocity inlet in free surface flow in transient simulation, I dont know accurately velocity so, instead velocity what I should entered, in intial condition and velocity inlet (note: I know flow rate in m3/sec)

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March 30, 2016, 08:01		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	The whole point of a boundary condition is that you know the conditions at that location so you don't need to model it, you can specify it and it becomes the boundary of the modelled region. If you cannot specify the flow conditions then you cannot put a boundary condition there. If you know the volume flow but you do not know the free surface level then consider a boundary where the flow wells up from below into a chamber connected to your domain. You can define the inlet pipe to have pure water at your flow rate, and it will determine the free surface level itself.