Fluid Height

robin781105 · February 24, 2014, 20:47

Dear expert:

I try to set the "Volume flow rate" boundary, so there needs to set both "Volume flow rate" and "Fluid Height".

There's a question, how can I set the "Fluid Height" when I fix the "flow rate" ?
How to know the true "normal flow depth" ?

JBurnham · February 28, 2014, 19:32

You have to hand-calculate it, or know it from field data. The variable you must input is the water surface elevation (distance from the z = 0 plane), not depth.

robin781105 · March 2, 2014, 10:21

Thanks JBurnham

It means I need to use Manning's equation to calculate the fluid depth?
Or Flow-3D has it's own equation to calculate fluid depth?

JBurnham · March 12, 2014, 21:03

You need to know what the depth is at the boundaries. If this is an imaginary situation, then use Manning's. If it's real, then use field data. FLOW-3D can't do it for you because Manning's requires modeling all the way from the nearest critical control. That might be many kilometers! If necessary, use HEC-RAS to estimate the steady-state depths of the boundaries.

robin781105 · March 18, 2014, 22:10

Thanks JBurnham！

I don't have the real data.

Is it feasible to determine the flow depth first then choose the water status to determine the discharge inflow?

y => Fr => Q=AV => get Q?

P.S.I'm a master student from Taiwan, my research is about weir flow.
If it possible, can I get your email and discuss with you?

February 24, 2014, 20:47	Fluid Height	#1
robin781105 New Member tsung han yang Join Date: Dec 2013 Posts: 12 Rep Power: 12	Dear expert: I try to set the "Volume flow rate" boundary, so there needs to set both "Volume flow rate" and "Fluid Height". There's a question, how can I set the "Fluid Height" when I fix the "flow rate" ? How to know the true "normal flow depth" ?

February 28, 2014, 19:32		#2
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	You have to hand-calculate it, or know it from field data. The variable you must input is the water surface elevation (distance from the z = 0 plane), not depth. spaudel likes this.

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March 2, 2014, 10:21		#3
robin781105 New Member tsung han yang Join Date: Dec 2013 Posts: 12 Rep Power: 12	Thanks JBurnham It means I need to use Manning's equation to calculate the fluid depth? Or Flow-3D has it's own equation to calculate fluid depth?

March 12, 2014, 21:03		#4
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	You need to know what the depth is at the boundaries. If this is an imaginary situation, then use Manning's. If it's real, then use field data. FLOW-3D can't do it for you because Manning's requires modeling all the way from the nearest critical control. That might be many kilometers! If necessary, use HEC-RAS to estimate the steady-state depths of the boundaries.

March 18, 2014, 22:10		#5
robin781105 New Member tsung han yang Join Date: Dec 2013 Posts: 12 Rep Power: 12	Thanks JBurnham！ I don't have the real data. Is it feasible to determine the flow depth first then choose the water status to determine the discharge inflow? y => Fr => Q=AV => get Q? P.S.I'm a master student from Taiwan, my research is about weir flow. If it possible, can I get your email and discuss with you?