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Re: [PSUBS-MAILIST] bionic propeller

Aha! Undulating propulsion. Hot topic of research in East Germany many years ago. It, and unsteady propulsion schemes in general, are fringe research topics because the unsteady (time-dependent) form of the relevant equations just isn't taught at the undergraduate level, where most of us leave off. Apparently, those unsteady solutions give theoretical numbers for efficiency that are very promising. Whether anybody has actually achieved those numbers - or anything close to them - is something that I have never been able to find out. Engineers take one look at the structural alterations that have to be made to accommodate such a system and generally turn away. 

I take it somebody is trying to raise money to try this full-scale?
The Kort nozzle is a variation on ducted propellers and fans in general - my sphere of expertise. It is not particularly efficient at cruise, but it produces very high forces under low-speed and static conditions, which is why it has become very popular for tugboats and other craft that need high thrust/hp at low speeds. Some small submersibles are equipped with Kort nozzles, which gives them lots of low-speed thrust to overcome their usually high hydrodynamic resistance, and protects the propeller from fouling, too. Good safety device for divers operating near the craft, too. 

Best,
Marc

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On 11/20/2010 8:47 AM, JimToddPsub@aol.com wrote:

Juergen,
If I'm correctly understanding what you're asking: Bionic propulsion is
basically a system that mimics the motion of a fish or marine mammal to
create thrust. Some have used piezo effect, some haven't, but I doubt
they will generally move beyond the research level anytime soon.
MIT has had a bionic propulsion research project for some years called
Robotuna. The only operational application I'm aware of was on an AUV or
ROV, and it went well (sorry I don't remember the name). It did have
lower energy consumption than a rotary propeller. At one time I saw a
robotic shark with a camera mounted on it (might have been during Shark
Week on Discovery Channel) that used bionic propulsion.
The most efficient propeller configuration I'm aware of is a Kort
nozzle, however I'll defer to the engineers and others in the group who
are much more knowledgeable.
Cheers,
Jim T
In a message dated 11/19/2010 5:54:53 P.M. Central Standard Time,
dbartsch2236@hotmail.com writes:

    I'd love to hear about this one too!

    David Bartsch

    ------------------------------------------------------------------------
    Date: Fri, 19 Nov 2010 23:23:28 +0000
    From: groplias2@yahoo.com
    Subject: [PSUBS-MAILIST] bionic propeller
    To: personal_submersibles@psubs.org

    Dear Pssubers
    does somebody have some experience with bionic propellers? It is
    said that they are more powerfull than normal propellers and very
    expensive but I want to know if somebody knows them first hand and
    confirm or not if they are so wonderfull as stated.
    Best wishes
    Juergen



    	


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