Fishes and dolphins are powerful propellers

This technology can work with any type vessels. There is no problem to submerge this propeller in the water.

 

You can see I do not use flapping fins. My propulsion device is a traveling wave generator. It can generate traveling waves running straight on or back. Fins can’t do it. Fins without a flexible fish or dolphin body are ineffective.

 

Well, now that we know that the propellor is inherently more efficient the fin, an interesting question is, why no creatures, beyond perhaps certain bacteria have evolved anything like propellors for propulsion, especially since propellors are also inherently mechanically more simple. Also interesting is how many marine creatures with probably fractional horsepower to commit to propulsion are able to accelerate faster than and swim circles around prop driven craft.

Perhaps there is more to this question than meets the eye or the conventional wisdom. Maybe it has something to do with the way wave motions propagate in fluids. Maybe on the molecular level the rules for viscous resistance change in the face of a sinusoidally applied force or motion. It certainly feels that way when you swim underwater using a dolphin stroke. It is almost surprising how much less resistance you feel and how much faster you go than say, kicking with your legs.

Dolphins and cetaceans actually swim at high speed for days. My guess is that they have evolved into a means for the application of force to a fluid medium which our simplistic physics doesn't yet comprehend. But we will eventually get it, if we keep trying to figure it out!

 

When looking at small prey fish or reef fish I see what appears to is an erratic swimming pattern, perhaps by design to disorientate predators. Let's call this swimming pattern "A".

Pattern "A" is useful in avoiding a predator and avoiding a straight flight/swim path. The zig zag affect of "A" may have it's uses in a military situation as in to avoid a torpedo. I'm going to guess that VladZenin and JonathanCole have little regard for this ability based on how they reacted to my question if a first effort went in circles, backwards or floundered. That's fine with me, one man's failure may be another success - I'll just let it go.

Pattern "B" focuses on straight-line speed yet is agile enough to catch prey trying to avoid it. Lets call this the Tuna, Pike and Dolphin approach. The only thing a school fish (Tuna), lone hunter (Pike), and mammal (Dolphin) have in common is that man has studied their swim patterns. Man likens himself to the predator, and identifies with the upper end of the food chain. It does not hurt that the performances of these three species are outstanding examples of evolutionary development.

Pattern "C" the silent stealthy Ray family, a prehistoric design enduring time and one with a sought after military attribute of acoustic stealth.

I can see development of A, B and C going on at the same time. Just as early powered flight sought development of the airplane and helicopter, and early cars sought development of the petrol engine, steam engine and electric drive motors.




.

 

Just as an aside, there are some very interesting (vortex) interactions between fish swimming in a school. Would you regard this as a swimming pattern in its own right?

Regards,
Leo.

 

Sure I would, I'm open minded, group/school swimming as it's own category "D" with it’s own unique consequences. As a novice on this topic I should be open-minded.

I can even see value in a swimming motion that mimics injury or mechanical difficulty to lure ones enemy into a trap or false sense of confidence. I've seen this done in many sports and competitions. I can see value in a design, which flounders on purposed just for that reason. Let's call that one "E".

 

I think creatures have not evolved anything like propeller because it could kill them and biotope. A human being creates more and more propellers and does not think about how dangerous they are for marine creatures and environment.
In my new thread: “How fast can we swim with a dolphin like propeller?” I have made an attempt to answer your others questions using our simplistic physics. Look at this thread please.

 

You can see I do not use flapping fins. My propulsion device is a traveling wave generator (see picture in a new thread: “How fast can we swim with a dolphin like propeller?”). It can generate traveling waves running straight on or back (see at a kinematics scheme of the pedal powered propulsion device). Fins can’t do it. You are right fin without flexible fish or dolphin body is ineffective. You are right regarding additional losses too. But we do not discuss this problem yet. I make attempt to illustrate and explain the principle of operation of the traveling wave generator. The mathematical proof of its efficiency is very complex. I will try to find more simple explanation.

 

The voice of knowledge. The voice of understanding. Nothing belittling in that. Just a valuable lesson for those able to learn.

 

Can'twait to see the reaction from those whose dreams will be damaged by knowledge...

 

I see you read my posts on this subject carefully. You will get to the point eventually.
(not practical.)

 

Propellers are not simple. They turn around 360 degrees. How do you propose a living organism manipulates its' limb/s to achieve rotational speeds for speeds fish reach with fins? Without screwing up muscle, arteries, and not to mention joints (remember the forces a propeller creates on its' axis).

And there is your answer why this is NOT the way to replace the propeller as well. Nature has found the way to generate force in a simpler way that places less stress on a fish's body. And doesn't tangle muscle and arteries while doing so but the trade-off is LOWER total efficiency. Or useability if you prefer. In case no one has noticed, great force and the speed can be achieved with comparatively small propellers and related mechanical structures. Not so with fins, flaps or alikes. Claims about percieved higher efficiency of sine, cosine or any other wave propulsion, are at best optimistic. There are no comparison studies in any of the links around that actually provide evidence to support these claims.
Not even as a comparison of speed or power per square meter of the surface.

If anything, the fact is that all known scientific experiments have confirmed that the principle is not PRACTICAL for applications in modern naval architecture.

Rotary movement will continue to dominate for its' advantages like small size, greater deliverable power and speed, lower vibrations. If anyone stands up to claim otherwise, they better have some hard evidence to support the claims, not 3D drawings of boats and waves. When THAT happens, I am sure that we'll all cross the floor.

 

Cheap, reliable, and handy auxiliary for small boats.

How about this idea?

Something like a scuba diversfoot fin tacked to a rudder on a small sailboat.

When not in use, all it causes is surface friction drag. Much unlike a non feathering propeller which either wants to keep turning or wants to twist the water it goes through it.

No long oar, paddle, or yulow shafts need to be stowed either (and they take up a LOT of space on a small sailboat).

And since it's a secondary means of propulsion, high efficiency is secondary to high convenience.

To move forward (sorry, no reverse. you got to get it right the first time) you just wag the tiller.

With the predominance of racing as a small sailboat use, it is easy to see why this hasn't been tried. If it worked, it would be outlawed at once.

(So much for those who insist that racing has done nothing but help small sailbot developement)

Bob

 

Hi Bob,
Your idea is not that bad. The fin or foil added to the rudder has to bee just right it works. I have tried it with good result.

 

As a fisheries biologist, I'll just add a few thoughts here...

Most fish do use their entire bodies for forward locomotion, although it is to varying degrees. Some of the fastest swimmers are tuna, and you will notice that they have relatively small caudal (tail) fins that move at very high speeds - they catch their prey primarily by running them down. A fish such as the pike, however, tends to move with long, undulating motions (like an eel) and is a relatively slow swimmer - they catch their prey primarily by ambush method.

Faster-swimming fish tend to have forked tails, leading to higher efficiency at faster swimming speeds. Slower-swimming fish have straight, unforked tails, leading to higher efficiency at slower swimming speeds. By the same token, river fish that hang out in the current will have forked tails, while river fish that hide behind rocks will not have forked tails.

Fish have very hydrodynamic bodies. Their slime coating, in addition to be used for protection from bacteria and sliding out of terrestrial predators paws, etc., also allows them to slide through the water easily. Additionally, fish scales have protrusions which are thought to allow them to slide through water more easily. This point was brought out in an article in the journal Nature circa 1993 or thereabouts, where they discuss hydrodynamic and aerodynamic drag. It seems surfaces with random protrusions had the least drag, surfaces with uniform protrusions had somewhat more drag, and smooth surfaces had very high drag. The concept is that water, and air to a lesser degree, forms vortices on the surface of the object moving through the water. These vortices roll up in a snowball effect (or like rolling up a rug) until they become large enough to break off and cause drag. The protrusions keep the vortices from building up and make the surface more 'slippery'. It's similar to the old golf ball effect. I believe some racing yachts have tried or are considering trying the technology on their hulls, but I don't know of any conclusive results yet. Chrysler attemped it on a vinyl roof of one of their Winston Cup race cars back around 1969, and it seemed effective until the vinyl padding was ripped away by wind at the speeds they were racing. Other applications would be commercial airliners, and moving fluids through pipelines more effieciently. But I digress...

Why do marine mammals (whales, dolphins, manatees, etc.) have horizontal tails rather than the vertical tails that fish sport? The most obvious explanation is that these mammals breathe surface air, and the horizontal tail is more efficient at moving them up and down in the water column, whereas the fishes' vertical tails allow them greater efficiency at swimming through the water horizontally.

Btw, I'm also a swimmer, and realize the speed and power of the dolphin kick. In most competitive swimming events, dolphin kick can only be used for a certain distance because of its proficiency, unless, of course, you are swimming the 'fly which requires the dolphin kick for its entirety.