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Ultrasonic cavitation

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Old   December 5, 2015, 12:38
Default Ultrasonic cavitation
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Christian
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Hello guys

I am currently working on a mixing reactor for Resin and Hardener. The mixing is happening through a sonotrode that emits Ultrasonic waves into the mixture.

Now i know that you can model cavitation in the CFX editor.

My Question is: how can i define that there is a plane that emits ultrasonic soundwaves? Do i have to create the sonotrode and insert it into the current setup? Or is there an easier solution?

Would be awesome if anyone with experience with something similar could post their experiences.

Kind Regards,
Christian
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Old   December 5, 2015, 18:43
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CFX has no built in model for this and I suspect no other CFD code does either. You are going to have to develop this yourself and implement it somehow.

Modelling the oscillations which create the micro-scale cavitation is unlikely to be practical on any computer in existence today. You are likely to have to use a separation of scales approach to model the overall effect of the ultrasonic cavitation - I assume you use it to accelerate mixing or accelerate the hardening reaction or something like that.
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Old   December 5, 2015, 20:07
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Hello Ghorrocks, thank you for that answer

well then i have to take a look how i will continue thanks for that!

And yes the ultrasonic waves and the induced cavitation is used to mix resin and hardener.

If anyone else has some more info or had a similar situation any help would be appreciated.
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Old   December 6, 2015, 05:16
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Have a look at acoustic modelling as the equations for that are quite different. There are also dedicated acoustics modelling software such as sysnoise. It will show you a much simpler wave of modelling acoustic waves than is possible in CFX. But note these assume linear waves and if the waves are triggering cavitation then the waves are definitely not linear.
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Old   December 13, 2015, 09:10
Default Cavitation as if through ultrasonic sound waves
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Ok so i had a talk with my supervisor and it is not necessary to simulate the soundwaves. The only thing we need is to make a simulation that approximates the cavitation through soundwaves.

Is it possible to do this by creating multiple domains and then modelling the pressure etc. as IF there were soundwaves advancing through the fluid? You would probably have to model multiple domains and define them exactly what you want them to do.

Would that be too time intensive or is there another easier solution to modell this problem?

I hope you understand what im asking here. Simplified im trying to do cavitation in a fluid that behaves as IF there were soundwaves but without the actuall simulation of the soundwaves just an approximated modell.
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Old   December 13, 2015, 17:28
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There appears to be two sides to this simulation: acoustics and the reaction accelerated by cavitation.

Acoustics can be modelled by CFX as the N-S equations do model acoustics. But for linear acoustic waves the equations can be simplified greatly and CFX does not have models for that. Software like sysnoise can model these simplified acoustics equations, and there will be open source equivalents as well. These acoustics solvers will solve an acoustics field much faster than CFX (like 1000 times faster, a few minutes versus weeks).

Cavitation acceleration of the reaction I will have to leave entirely up to you. You are going to have to research the literature to understand how this works and how to model it. It is not my field of expertise.
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Old   December 14, 2015, 07:55
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Hello again ,

ok thanks for that. I already started doing some research and found a pretty good introduction for that. Thanks for the help!!!
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