Does Water Depth Affect Marine Propeller Resistance and Cavitation?

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Discussion Overview

The discussion centers on the effects of water depth on marine propeller resistance and cavitation, exploring whether varying water column heights (5m vs 35m) influence torque requirements and energy release associated with cavitation phenomena. The scope includes theoretical considerations and practical implications for marine propulsion systems.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions the difference in torque required to maintain a constant RPM of a marine propeller at different water depths.
  • Another participant suggests that water's incompressibility means depth may not significantly affect torque, highlighting that surface proximity can lead to cavitation due to air impact.
  • It is noted that cavitation may be reduced at greater depths due to increased pressure.
  • A participant raises a question about optimizing energy release from cavitation, considering whether a shallow or deep water column would be more effective for generating energy from cavitation bubbles.
  • There is a request for clarification regarding what is meant by "energy release," with a later specification that thermal energy release is intended.
  • One participant interprets the goal as wanting to eliminate cavitation to improve efficiency, while another clarifies the intention to create cavitation for heating purposes.

Areas of Agreement / Disagreement

Participants express differing views on the implications of water depth for cavitation and torque requirements, with no consensus reached on the optimal conditions for energy release from cavitation.

Contextual Notes

Assumptions regarding the relationship between water depth, pressure, and cavitation effects remain unresolved, as do the specific conditions under which energy release is evaluated.

copria
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Is there a noticable diffence in torque required to spin a marine propeller at a constant rpm (say 2000rpm) when under a different water column? (5m vs 35m)
 
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Not much, water isn't very compressible.
ussually the problem is running them near the surface, the impact from air onto the surface of the water causes cavitation.
 
note, however, that cavitation is reduced with depth because of the pressure.
 
If I want to optimize the energy release from cavitation would it be better to have a shallow water column (producing larger amounts of cavitation) or a deep water column (larger force collapsing the cavitation bubble)?
or
Would both cases yield the same energy release?

assuming the propeller is at a constant speed
 
Last edited:
thermal energy release
 
You mean you want to eliminate cavitation, right? Higher pressure reduces/eliminates cavitation, reducing energy/efficiency loss.
 
No, I want to create cavitation (like a cavitation water heater).

Sorry I did not specify earlier.
 

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