important: spillway with aerator device

flow_CH · March 1, 2013, 05:34

Hello.

I have very important question.
I have to simulate a spillway with aerator device, in CFX.(for prevention of cavitation)
Can CFX 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

flow_CH · March 1, 2013, 10:20

nobody can't help me?

ghorrocks · March 3, 2013, 06:33

Yes, CFX can do this but it will be a tricky multiphase model which will require careful validation and experimental work to get accurate. I hope you have several months to work on this.

flow_CH · March 3, 2013, 09:30

Quote:

Originally Posted by ghorrocks

Yes, CFX can do this but it will be a tricky multiphase model which will require careful validation and experimental work to get accurate. I hope you have several months to work on this.

several months?! why? I have to simulate that.
can flow 3d do that? i don't have any experience in CFX modeling.

ghorrocks · March 3, 2013, 17:35

You need to be able to get the following physics all working correctly for you to have an accurate simulation:
* Air entrainment in a fast flowing water stream
* Air suppression of cavitation
* Cavitation
* free surface flow with high aerated water

and probably more. Any one of these models will take a few weeks to get working (if you know what you are doing), and getting them to work together will take a while longer again.

This is complex stuff. It will take a lot of research and then validation & verification before you have reliable results. I hope you were not expecting to press the "aeration of dam spillway" button and it would all just work.

And no, switching to another code will not help. You have to understand the physics of what you are modelling before you have any hope of modelling it correctly, regardless of which CFD code you use.

ghorrocks · March 3, 2013, 17:37

To be a bit more useful - I recommend you simplify your model to soemthing more practical. Can you simplify the model but keep the essential physics?

flow_CH · March 4, 2013, 01:14

Quote:

Originally Posted by ghorrocks

To be a bit more useful - I recommend you simplify your model to soemthing more practical. Can you simplify the model but keep the essential physics?

Thanks.
I have experimental results about this spillway and i will calibrate numerical results with experimental results. I hope i can do that in CFX because i don't have any experience in CFX.

ghorrocks · March 4, 2013, 05:42

CFX can do this model, but as I have already said this is a challenging model so do not expect to get answers over night. You will need experimental results to calibrate to.

March 1, 2013, 05:34	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 CFX.(for prevention of cavitation) Can CFX 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

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March 1, 2013, 10:20		#2
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	nobody can't help me?

March 3, 2013, 06:33		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Yes, CFX can do this but it will be a tricky multiphase model which will require careful validation and experimental work to get accurate. I hope you have several months to work on this.

March 3, 2013, 17:35		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	You need to be able to get the following physics all working correctly for you to have an accurate simulation: * Air entrainment in a fast flowing water stream * Air suppression of cavitation * Cavitation * free surface flow with high aerated water and probably more. Any one of these models will take a few weeks to get working (if you know what you are doing), and getting them to work together will take a while longer again. This is complex stuff. It will take a lot of research and then validation & verification before you have reliable results. I hope you were not expecting to press the "aeration of dam spillway" button and it would all just work. And no, switching to another code will not help. You have to understand the physics of what you are modelling before you have any hope of modelling it correctly, regardless of which CFD code you use.

March 3, 2013, 17:37		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	To be a bit more useful - I recommend you simplify your model to soemthing more practical. Can you simplify the model but keep the essential physics?

March 4, 2013, 05:42		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	CFX can do this model, but as I have already said this is a challenging model so do not expect to get answers over night. You will need experimental results to calibrate to.