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important: spillway with aerator device

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Old   February 25, 2013, 01:59
Default important: spillway with aerator device
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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 likes this.

Last edited by flow_CH; February 25, 2013 at 08:26.
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Old   February 25, 2013, 10:23
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Quote:
Originally Posted by flow_CH View Post
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.
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Old   February 25, 2013, 10:54
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Quote:
Originally Posted by Jing_min View Post
Hi
It seems that the software is not capable of that.
Only free surface aeration is possible.
are you sure this isn't possible?
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Old   February 25, 2013, 13:40
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Originally Posted by flow_CH View Post
are you sure this isn't possible?
As far as I know.
But I would be glad if it happens!!!!!
Please let me know.
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Old   February 25, 2013, 13:59
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Is the ramp (eg. offset,groove or ...) Sufficient for prevention of cavitation for simulating in flow 3D?(without injection air into the ramp)
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Old   February 25, 2013, 17:05
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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.
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Old   February 26, 2013, 02:04
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someone give me confidence about this modeling, please.
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Old   February 26, 2013, 13:32
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Originally Posted by flow_CH View Post
someone give me confidence about this modeling, please.
You can contact FlowScience to have a consult.
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Old   February 27, 2013, 00:53
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Is there a difference between the chute with ramp(without injection air into the ramp) and without ramp answers in flow 3D?
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Old   March 1, 2013, 05:24
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please help.
someone give me confidence about this modeling, please.
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Old   March 2, 2013, 01:48
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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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Old   March 4, 2013, 11:17
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It can be done - trust JBurnham on this one.
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Old   March 4, 2013, 16:21
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Quote:
Originally Posted by JBurnham View Post
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?
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Old   April 6, 2013, 05:02
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Quote:
Originally Posted by flow_CH View Post
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?
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Old   April 6, 2013, 22:45
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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.
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Old   April 7, 2013, 03:11
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can flow3d pull the air into the ramp without modeling artificial entrainment of air?
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