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Old   May 24, 2002, 07:30
Default cavitation
  #1
Matthias
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Hi there,

how can i find out easily if a flow through a jet or something similar cause erosion because of bubble impact in near wall regions or not.

for example:

-incompressible fluid

-steady state

-k-eps modell

-axissymm pipe-jet-pipe flow

results:

because of high velocities in the smallest Area there are regions downstream of the smallest gap where the static pressure is below the vapour pressure of the fluid and cavitation could exists.

questions:

-> how can i find out if the bubbles produced in the low pressure region will impact in the near wall regions

-> what are the criterias for erosion caused by cavition

-> are there simply equations to determine the critical time necessary for a impact in near wall regions, or equations for the time which a bubble needs to growth to a critical radius

-> is there a method to predict a erosion caused by cavitation

regards

Matthias

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Old   May 24, 2002, 09:22
Default Re: cavitation
  #2
Joern Beilke
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You might run your calculation using a cavitation modell. These models are far away from beeing good but ...
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Old   May 24, 2002, 09:24
Default Re: cavitation
  #3
Matthias
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i know, but i have not the possibility to use a cavitation model. Is there no other way to predict erosion.

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Old   May 24, 2002, 09:55
Default Re: cavitation
  #4
Alton Reich
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Matthias,

Our CFD-ACE+ has a robust, validated cavitation model that can predict bubble formation and collapse. It would allow you to see if there is bubble collapse in the vicinity of walls.

You would then have the ability to use the simulation results to make some educated guesses about the potential for erosion. "Prediction" of erosion is tricky because of the factors involved (including things like material type, surface treatment, and others). We have some plans to add an erosion prediction model to CFD-ACE+, but (like many other things) it's a matter of getting around to it.

Regards, Alton
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Old   May 24, 2002, 10:02
Default Re: cavitation
  #5
Matthias
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Dear Alton,

is there no other way (without a cavitation model and analytical -> something easy) to guess where the bubbles will implode and where the imploding bubbles cause erosion.

best regards

Matthias
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