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Marine Propeller Resistance

  1. Mar 26, 2009 #1
    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)
     
  2. jcsd
  3. Mar 26, 2009 #2

    mgb_phys

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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.
     
  4. Mar 26, 2009 #3

    russ_watters

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    note, however, that cavitation is reduced with depth because of the pressure.
     
  5. Mar 27, 2009 #4
    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: Mar 27, 2009
  6. Mar 27, 2009 #5

    russ_watters

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    Energy release? What energy release?
     
  7. Mar 28, 2009 #6
    thermal energy release
     
  8. Mar 28, 2009 #7

    russ_watters

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    You mean you want to eliminate cavitation, right? Higher pressure reduces/eliminates cavitation, reducing energy/efficiency loss.
     
  9. Mar 28, 2009 #8
    No, I want to create cavitation (like a cavitation water heater).

    Sorry I did not specify earlier.
     
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