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I'm new here and would like to ask where the cavitation would happen in my design.

ThanksRim Drive Technology

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    $\begingroup$ You need to specify things like velocity, pressure drop, viscosity etc because if the velocity is low enough and the pressure drop low enough then cavitation won’t happen. $\endgroup$
    – Solar Mike
    Jan 12 '20 at 18:36
  • $\begingroup$ This is an older prototype and not able to share my latest work as the file is to large. To respond to your request and if some was to take a closer look a the design and take in account a few simple rules in fluid mechanics ,this is a snap shot of my design . The inlet vanes are matched to impeller for optimum angle of attach and minimize stagnation points of impeller and having a fluid always entering at a constant angle regardless of velocity and with rim drive design and impeller acting on the fluid in a homogeneous force and with the outlet vanes bringing back the fluid flow to a laminar. $\endgroup$ Jan 12 '20 at 19:02
  • $\begingroup$ I drove an axial flow pump from zero to cavitation and plotted the resulting dimensionless curves... so the variations of inlet pressure above or below atmospheric make the guessing of how your pump will behave even riskier than putting money down at the casino... $\endgroup$
    – Solar Mike
    Jan 12 '20 at 19:48
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Your pump is an axial flow pump. I'm not an axpert, but from skimming literature it appears that the most relevant form of cavitation ins common ax flow pumps appears at the tips of the blades (where speed is highest, possibly aided by shear with the pump housing, tip vortex cavitation is the search term). Since the inlet of ax flow pumps is typically fairly wide, this is not the palce where you'd expect caviation. So in your design, I would investigate the areas directly upstream and downstream of the rotorspecifically between the static vanes and the guiding vanes and near the outter edges of the rotor.

Another common point where cavitation occurs is the inlet. However in your design there appears to be no real reduction in free diameter along the pump, so the axial component of flow velocity should be pretty constant. My guess is that the inlet won't see much cavitation.

But at the end of the day these are (not very well) educated guesses and you need to do CFD and physical experiments to verify your design.

Edit to add:
The OP stated in a (removed) comment that CFD is out of their reach. The (in many ways beter!) alternative is a physical test. There's no other way to determine the characteristics of of a novel impeller. The good news is that you can somewhat extrapolate from from a small prototype using affinity laws (Though I assume your pump will always be pretty small, because of the seals)

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Cavitation happens where there is pressure drop usually near the eye of an impeller of a pump or after sharp turns in the flow caused by the blades or the geometry of the pump on the interior, low pressure, side of the bend.

They can even happen in our blood-stream sometimes.

The partial vacuum encourages the formation of bubbles (cavitation) that travel with the flow until they reach a high-pressure zone where the may instantaneously implode and damage the surface or part near to this zone.

There are two types of cavitation: suction and discharge. You need to look for suction near the inlet and discharge cavitation inside the pump housing near the discharge.

Simulation software also can predict the cavitation area.

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