important: spillway with aerator device

flow_CH · February 25, 2013, 01:59

Hello.

I have very important question.
I have to simulate a spillway with aerator device, in Flow 3D.(for prevention of cavitation)
Can flow 3D simulate this chute with artificial injection air into the ramp?
or the ramp (eg. offset,groove or ...) is Sufficient for prevention of cavitation?(without injection air into the ramp)
see this pic

Jing_min · February 25, 2013, 10:23

Quote:

Originally Posted by flow_CH

Hello.

I have very important question.
I have to simulate a spillway with aerator device, in Flow 3D.(for prevention of cavitation)
Can flow 3D simulate this chute with artificial injection air into the ramp?
or the ramp (eg. offset,groove or ...) is Sufficient for prevention of cavitation?(without injection air into the ramp)
see this pic

Hi
It seems that the software is not capable of that.
Only free surface aeration is possible.

flow_CH · February 25, 2013, 10:54

Quote:

Originally Posted by Jing_min

Hi
It seems that the software is not capable of that.
Only free surface aeration is possible.

are you sure this isn't possible?

Jing_min · February 25, 2013, 13:40

Quote:

Originally Posted by flow_CH

are you sure this isn't possible?

As far as I know.
But I would be glad if it happens!!!!!
Please let me know.

flow_CH · February 25, 2013, 13:59

Is the ramp (eg. offset,groove or ...) Sufficient for prevention of cavitation for simulating in flow 3D?(without injection air into the ramp)

JBurnham · February 25, 2013, 17:05

You can inject the air using 1-fluid, free-surface flow in several ways. All of them require 'density evaluation: 1st- or 2nd-order approximation to the transport equation' option. I would also use the drift-flux physics.

The air can be injected using a mass-momentum source with density set to that of air. Or it can be entrained using Air Entrainment physics, but that requires calibrating the air entrainment rate coefficient, so I would recommend just using the mass/momentum source. You need to know the rate of air injection for this option. If you don't know the rate of air injection, and can't even guess at it, then you can't model this situation.

I wouldn't recommend using the cavitation model for this case: just look at the pressures near surfaces and check to see if they are below cavitation pressure.

flow_CH · February 26, 2013, 02:04

someone give me confidence about this modeling, please.

Jing_min · February 26, 2013, 13:32

Quote:

Originally Posted by flow_CH

someone give me confidence about this modeling, please.

You can contact FlowScience to have a consult.

flow_CH · February 27, 2013, 00:53

Is there a difference between the chute with ramp(without injection air into the ramp) and without ramp answers in flow 3D?

flow_CH · March 1, 2013, 05:24

please help.
someone give me confidence about this modeling, please.

flow_CH · March 2, 2013, 01:48

Dear all

i just have three monthes to do this project.
Please answer this three questions. Answers to these questions will help me a lot.
1- What points are in this project that distinguish this model from other models? (the models without injection air into the ramp)
2- What boundary conditions should i define into the flow 3D? I think the most difficult parts of the software are boundary conditions and meshing.
3- How air can inject into the ramp?
thanks

dmilano · March 4, 2013, 11:17

It can be done - trust JBurnham on this one.

flow_CH · March 4, 2013, 16:21

Quote:

Originally Posted by JBurnham

You can inject the air using 1-fluid, free-surface flow in several ways. All of them require 'density evaluation: 1st- or 2nd-order approximation to the transport equation' option. I would also use the drift-flux physics.

The air can be injected using a mass-momentum source with density set to that of air. Or it can be entrained using Air Entrainment physics, but that requires calibrating the air entrainment rate coefficient, so I would recommend just using the mass/momentum source. You need to know the rate of air injection for this option. If you don't know the rate of air injection, and can't even guess at it, then you can't model this situation.

I wouldn't recommend using the cavitation model for this case: just look at the pressures near surfaces and check to see if they are below cavitation pressure.

JBurnham: "If you don't know the rate of air injection, and can't even guess at it, then you can't model this situation."

But There is no anything about the rate of air injection in the experimental results that i have. The air entrainment reason is suction of flow velocity or self aeration or something like that. in this situation i can't simulate that?

flow_CH · April 6, 2013, 06:02

Quote:

Originally Posted by flow_CH

JBurnham: "If you don't know the rate of air injection, and can't even guess at it, then you can't model this situation."

But There is no anything about the rate of air injection in the experimental results that i have. The air entrainment reason is suction of flow velocity or self aeration or something like that. in this situation i can't simulate that?

Dear all

i just have two monthes to do this project.
please help.
There is no anything about the rate of air injection in the experimental results that i have. The air entrainment reason is suction of flow velocity or self aeration or something like that. in this situation i can't simulate that?

JBurnham · April 6, 2013, 23:45

You can model self-aeration - but you should calibrate the air rate entrainment coefficient so you get the correct rate of self-entrainment. In order to do that you must have some idea of what the amount of entrained air was in the experiment. Please refer to the User Manual and the air entrainment Tech Note on the FLOW-3D User Site for details on air entrainment at turbulent free surfaces.

flow_CH · April 7, 2013, 04:11

can flow3d pull the air into the ramp without modeling artificial entrainment of air?

February 25, 2013, 01:59	important: spillway with aerator device	#1
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	Hello. I have very important question. I have to simulate a spillway with aerator device, in Flow 3D.(for prevention of cavitation) Can flow 3D simulate this chute with artificial injection air into the ramp? or the ramp (eg. offset,groove or ...) is Sufficient for prevention of cavitation?(without injection air into the ramp) see this pic farshid and elyasmin like this. Last edited by flow_CH; February 25, 2013 at 08:26.

March 2, 2013, 01:48		#11
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	Dear all i just have three monthes to do this project. Please answer this three questions. Answers to these questions will help me a lot. 1- What points are in this project that distinguish this model from other models? (the models without injection air into the ramp) 2- What boundary conditions should i define into the flow 3D? I think the most difficult parts of the software are boundary conditions and meshing. 3- How air can inject into the ramp? thanks Last edited by flow_CH; March 2, 2013 at 02:15.

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February 25, 2013, 13:59		#5
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	Is the ramp (eg. offset,groove or ...) Sufficient for prevention of cavitation for simulating in flow 3D?(without injection air into the ramp)

February 25, 2013, 17:05		#6
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	You can inject the air using 1-fluid, free-surface flow in several ways. All of them require 'density evaluation: 1st- or 2nd-order approximation to the transport equation' option. I would also use the drift-flux physics. The air can be injected using a mass-momentum source with density set to that of air. Or it can be entrained using Air Entrainment physics, but that requires calibrating the air entrainment rate coefficient, so I would recommend just using the mass/momentum source. You need to know the rate of air injection for this option. If you don't know the rate of air injection, and can't even guess at it, then you can't model this situation. I wouldn't recommend using the cavitation model for this case: just look at the pressures near surfaces and check to see if they are below cavitation pressure.

February 26, 2013, 02:04		#7
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	someone give me confidence about this modeling, please.

February 27, 2013, 00:53		#9
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	Is there a difference between the chute with ramp(without injection air into the ramp) and without ramp answers in flow 3D?

March 1, 2013, 05:24		#10
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	please help. someone give me confidence about this modeling, please.

March 4, 2013, 11:17		#12
dmilano Member Join Date: Mar 2012 Posts: 72 Rep Power: 14	It can be done - trust JBurnham on this one.

April 6, 2013, 23:45		#15
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	You can model self-aeration - but you should calibrate the air rate entrainment coefficient so you get the correct rate of self-entrainment. In order to do that you must have some idea of what the amount of entrained air was in the experiment. Please refer to the User Manual and the air entrainment Tech Note on the FLOW-3D User Site for details on air entrainment at turbulent free surfaces.

April 7, 2013, 04:11		#16
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	can flow3d pull the air into the ramp without modeling artificial entrainment of air?