Fishes and dolphins are powerful propellers

[VladZenin]

I was wrong putting the picture of a catamaran. Travelling wave propeller can be installed on any kind of vessels. Why do you think that the wave sheet is moved with fixed amplitude? It is well known that the amplitude of oscillation of the swimming fish and dolphin body increases from the head to the tail. It is easy to realize in a propulsion device (see picture). What do you think about efficiency this propulsion device? What a difference in exit velocity compared to the free stream velocity will be?
See also "How fast can we swim with a dolphin like propeller?"
http://boatdesign.net/forums/showthread.php?t=8257

[VladZenin]

Originally Posted by Guillermo

Ambulocetus, the walking whale!
http://dsc.discovery.com/convergence...to2_zoom9.html
http://en.wikipedia.org/wiki/Ambulocetus

I knew about it. I am a geologist by my first profession.

[VladZenin]

Originally Posted by mrdancer

I would lean toward using a vertical wave (side-to-side) as opposed to the up-and-down wave. My reasoning is a more stable vessel, particularly at speed, where the bow has no extraneous input on its entry into the water. As for side-to-side wave motion, effect on vessel can be minimized with twin adjacent drives, each canceling the other and possibly enhancing overall output (think frog kick). I think this would be much easier to design then an up-and-down system that produces no unwanted effects.

Have a look at the picture above. You can use this propulsion device in a vertical position too.

[water addict]

The most efficient way to go from A to B is of course the transporter like that used in Star Trek. You just need some dilithium crystrals and a matter/anti-matter power source.

[JonathanCole]

Originally Posted by VladZenin

What do you think about efficiency this propulsion device?

Vlad,

I think to make the travelling wave propulsion device practical, it is not appropriate to utilize an expensive, complex mechanical linkage. With mechanical devices, the more moving parts, the more places for failure. Perhaps a piezoelectric device (material bends with application of voltage). Such devices are already used to make fans for electronic devices. Another approach might be the use sheets of material that expand lengthwise with the application of electricity. Two such sheets bonded together would form a curve when only one is activated. Activate the opposite side and the curve reverses.

Aloha,

Jonathan

[tspeer]

Originally Posted by VladZenin

...What do you think about efficiency this propulsion device?

My point is, you should be telling us. Nobody can just look at something and make a statement about its efficiency. At the preliminary stage, one's estimate necessarily has to be crude because you have to make a lot of assumptions to fill in for data you don't have. But I think you ought to make the effort to assess it.

What a difference in exit velocity compared to the free stream velocity will be?

To some extent, you specify what the exit velocity has to be. In order to power a given vessel at a given speed, you need a certain thrust. You can get the thrust with a high exit velocity and small exit area, or vice versa. The first step the designer has to do is chose these parameters and then see if the rest of the system is consistent with them.

[VladZenin]

I don’t need to do this. Mother-Nature have done this for us.

[VladZenin]

Originally Posted by water addict

The most efficient way to go from A to B is of course the transporter like that used in Star Trek. You just need some dilithium crystrals and a matter/anti-matter power source.

Storm of applause

[VladZenin]

Originally Posted by JonathanCole

Vlad,

I think to make the travelling wave propulsion device practical, it is not appropriate to utilize an expensive, complex mechanical linkage. With mechanical devices, the more moving parts, the more places for failure. Perhaps a piezoelectric device (material bends with application of voltage). Such devices are already used to make fans for electronic devices. Another approach might be the use sheets of material that expand lengthwise with the application of electricity. Two such sheets bonded together would form a curve when only one is activated. Activate the opposite side and the curve reverses. Aloha, Jonathan

It is very interesting. Do you know performance attributes of a piezoelectric effect and expanding lengthwise with the application of electricity? What size of the expanding do you expect to achieve?

[JonathanCole]

Originally Posted by VladZenin

It is very interesting. Do you know performance attributes of a piezoelectric effect and expanding lengthwise with the application of electricity? What size of the expanding do you expect to achieve?

There is a lot about this on the Internet. Here is a good departure point:
http://widget.ecn.purdue.edu/~CTRC/r...piezofans.html
Maybe this has relevance to Kjells fish tail propulsion as well. It seems that the piezo material flexes only a tiny amount with application of voltage, but also requires very little energy. Two pieces bonded as I said earlier could possibly flex and curve quite a lot due to the constraint of one plane on the other. In any case, the traveling wave may be better if it has low amplitude and high frequency as energy is applied most advantageously at high frequencies.

[VladZenin]

Yes, the piezo material flexes only a tiny amount with application of voltage. But it may be good for making toys.

[kjell]

[quote=JonathanCole]
Maybe this has relevance to Kjells fish tail propulsion as well. QUOTE]

It is very interesting. I maybe can use this technique in small Tail-Jets for mini submarines.

[JonathanCole]

[quote=kjell]

Originally Posted by JonathanCole

Maybe this has relevance to Kjells fish tail propulsion as well. QUOTE]

It is very interesting. I maybe can use this technique in small Tail-Jets for mini submarines.

Actually the illustration for the piezoelectric fan also suggests that the same flapping tail drive could be set up using electromagnetic coils on two sides of a magnetic material embedded in the base of the tail. This could be switched electronically and would eliminate the complexity of a mechanical drive which might be a very practical improvement both from a cost and durability perspective.

[kjell]

Originally Posted by JonathanCole

Actually the illustration for the piezoelectric fan also suggests that the same flapping tail drive could be set up using electromagnetic coils on two sides of a magnetic material embedded in the base of the tail. This could be switched electronically and would eliminate the complexity of a mechanical drive which might be a very practical improvement both from a cost and durability perspective.

This is an electro magnetic tail drive I was testing some years ago.

[VladZenin]

I see my travelling wave propulsion devices do not excite curiosity. I understand they are complicated and bulky. My ultimate aim was to disclose the idea of this kind of propulsion and show some specific engineering solutions. I think there are lots of physical principles that could be used for travelling wave generation. They should be uncovered when first boat models will show high performance attributes.