Magnus effect for ship propulsion

Discussion in 'Propulsion' started by 1J1, Mar 6, 2017.

  1. 1J1
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    1J1 Senior Member

    Hi! Recently I came across this patent - https://www.google.com/patents/EP1155956A2?cl=en - use of Magnus effect for propelling the ship. Basically, a rotating cylinder which creates a flow & difference in pressures by itself, as I understand from looking at those pics. Is such actually possible? :confused:
     

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  2. TANSL
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    TANSL Senior Member

    Nearly a century ago was launched the first ship with Flettner rotors, that take advantage of Magnus effect.
    So the answer to the question is, YES, it is possible. Profitable?, I do not know.
     
  3. 1J1
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    1J1 Senior Member

    That's different, cause Flettner rotors operate only if there's wind acting on them.
     
  4. Ilan Voyager
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    Ilan Voyager Senior Member

    Make a serious search in Internet. Several boats have been made, one in 1928, another by Cousteau the boat Alcyon. None has been very successful. Many drawbacks. There is a thread in the forum.
    When an invention does not become mainstream, it's because there are problems, or there are not applications...People in engineering are not conservatively stupid (in ideology and politics it's different) but practical.
     
  5. TANSL
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    TANSL Senior Member

    1J1, it is that the system that you propose acts in the vacuum?.
     
  6. daiquiri
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    daiquiri Engineering and Design

    It works as a thought experiment, but not very well in practice. I had made several CFD analyses of similar rotor arrangements (didn't know about the existance of this patent) and the results can be summed up as follows:
    1) At zero forward speed, no steady-state solutions were possible. Very small and highly oscillating thrust force was created, and the efficiency was below ridiculous.
    2) At low forward speed, no steady-state solutions were possible. Huge alternating (karman-style) vortices were continuously created at random points on the sides of the propulsor, thus making it very inefficient, vibration-inducing and possibly uncontrollable.
    3) At higher forward speeds, the net thrust was negative. In other words, it was a drag machine.

    As a matter of fact, that patent is dated 1996, 20 yrs ago - do you currently see ships, boats or airplanes pushed by this propulsion system? I have never seen any.

    Cheers


    Edit:
    Didn't know about that one either. But are you sure that it was the same principle? The only info I could find about Custeau's boat named Alcyone were relative to a flettner-rotor sailboat.

    Re-edit:
    "Attinent" was supposed to mean "pertinent", in my ignorant dictionary. Credits to Philsweet for bringing it to my attention. :)
     
    Last edited: Mar 6, 2017
  7. philSweet
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    philSweet Senior Member

    You may want to look at the Voith Turbo Fin.

    [​IMG]
     
  8. Barry
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    Barry Senior Member

  9. daiquiri
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    daiquiri Engineering and Design

    The leading-edge rotating cylinder is a high-lift device, not a propulsion device. As such, it is IMO not very attinent to the OP.
    They have been concieved back in 1960's and, though promising on paper, have never become a mainstream high-lift technology due to important inherent mechanical and structural issues.

    Regarding the use of twin rotating cylinders for propulsion, the main problem is that whatever configuration one choses they remain hydrodynamically just two vortices superimposed on the uniform flow field. It means that they can essentially be arranged as:
    1) A pair of counter-rotating vortices, which is seen by the far-field flow as a doublet (http://web.mit.edu/fluids-modules/www/potential_flows/LecturesHTML/lec1011/node24.html). But a doublet flow cannot generate thrust, not even in the ideal case. It can generate drag though, in the real case.
    2) A pair of co-rotating vortices, which is seen as a single vortex (http://web.mit.edu/fluids-modules/www/potential_flows/LecturesHTML/lec1011/node21.html) with a total vorticity equal to the sum of vorticities of two elemental vortices. In this case a lift force can be generated, which is perpendicular to the upstream flow. But a perpendicular force cannot generate thrust, again.

    Adding a fixed vane or foil doesn't change a thing. A foil is still a vortex in the far field, so instead of 2-vortex system, it becomes a 3-vortex system. Again, only a force perpendicular to the flow (lift) is created or modified.

    In order to create a thrust, a separate system with the axial action on the flow (i.e. a prop, a jet or else) has to be introduced.
     
  10. Rastapop
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    Rastapop Naval Architect

  11. Rastapop
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    Rastapop Naval Architect

    This is how flettner rotors work. They require flow perpendicular to the direction of travel: wind.
     
  12. rwatson
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    rwatson Senior Member

    Couple of inaccuracies here-
    1) "Cousteau the boat Alcyon" was not a Flettner rig. This is covered extensively in the thread mentioned below. I also saw a detailed documentary hosted by Costeau that explained the principle, and the 'sail' definitely did not rotate.
    2) "one in 1928," TWO in 1928, one E Ship 1 on the 2nd of August 2008.
    http://www.thiiink.com/history-of-flettner-rotor/
    3) "None has been very successful" In the main Flettner thread, the last few entries are of Scandinavian ferries which have installed wind rotors in the past few years, to take advantage of particular routes and wind patterns. The second rotor was added after extensive sea trials. The principle is sound, the economics vary, but work in some scenarios.


    The thread on Wind Rotors is
    http://www.boatdesign.net/forums/bo...again-flettner-rotor-ship-launched-24081.html


    As for 'below water' application, that's news to me, for propulsion. Surely it would require a secondary flow like the Flettner 'sail', as was previously mentioned.

    Flettner did participate in inventing the below the water 'trim tab' which features on large ship rudders, ( and planes) but it wasn't propulsive.
    https://en.wikipedia.org/wiki/Servo_tab
     
  13. daiquiri
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    daiquiri Engineering and Design

    They require even more than that. A keel (or another, underwater rotor) is necessary too, or else there would be no reference frame in which the rotor lift could be transformed into thrust.
    Just as sails do, and just as the device in the OP does. :)
     
  14. Ilan Voyager
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    Ilan Voyager Senior Member

    The Alcyone sails whatever the Cousteau society claims are different from the Fletner rotor, the classic rotating tube.

    All the pages of Cousteau society about Alcyone are shut down. All has disappeared. Happily there is a wiki.
    https://en.wikipedia.org/wiki/Turbosail

    I have seen this boat very closely and I knew people who sailed on it. The famous sails were in fact expensive in-commodities. Happily the Alcyone had two 200 HP engines which did 98% of the job through classic propellers.

    All the papers presented (look at the end of the wiki) were wishful thinking, anticipating the solution of the problems and dreaming awake. The first big evident problem is the drag and behavior in bad sea. You can imagine all that pounding and bouncing in a bad shop, with the masts tops moving over 3 meters. It's also indecently heavy. The other problem is the extreme complexity for a small or negative advantage like with the DynaRigs.

    And you can imagine trying to move a cargo with that on the deck...In fact kites for downwind are simpler and more efficient, but with so few people on the cargos now, a few officers and a bunch of underpaid Philippinos for maintaining the ship and cooking, there is no time nor wish.
    I do not see the captain, already struggling with a tight schedule, waste time tinkering with a kite and all the potential problems or any sail on the ship. The crewmen are almost as exploited as an undocumented Mexican in a Californian strawberry field, or a Bengali woman in a clothes factory.
     

  15. TANSL
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    TANSL Senior Member

    For you who like to be very accurate in the use of the language, just a comment: the artifact is called by some a "Flettner rotor".
    You're welcome.
     
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