#50133: — 11/21  at  07:02 PM
Axiom, note that the high (90%+) efficiencies are only for jet efficiency. The total cycle efficiency is around 40%: not unexpected given that it's drawing water in from the wrong end and has a pulsed rather than continuous cycle (around 20% of the time is opening/closing valves - worse than a pulse-jet rocket motor.)

The squid is using cool propulsion tech, but it isn't very efficient compared with, say, fish.

Trackback: Jet flow in steadily swimming adult squid Tracked on: squidblog.net (70.86.157.90) at 2005 11 21 20:11:39
Any cephalophile engineers out there? The frightening prolific PZMyers has helpfully alerted us to a recent paper in the Journal of Experimental Biology, which looks in detail at Jet flow in steadily swimming adult squid. However, just like PZMyers...

#50167: — 11/21  at  11:58 PM
Yeah, as a water engineer, I agree that the squid is very poorly designed. A pulsating ball of muscles is an idiotic way of propulsion, any fish can do better. The reasonable explanation for this inefficiency is that the squid is descended from a kind of jellyfish with pneumatophora that had to do its best to get around what it had. In that sense, I think, the squid maximizes the efficiency of its basic design, exploiting all its possibilities including vortex creation, but it has arrived to a dead end. It cannot movilize itself faster. The only way it can improve its design is by developing fins. It is be interesting to study why no squid did that up to now. All in all, it is a beautiful demonstration of evolution vs design.

#50171: ekzept — 11/22  at  12:24 AM

It is be interesting to study why no squid did that up to now. All in all, it is a beautiful demonstration of evolution vs design.

um, because there's (a) no optimization in evolution, and (b) no selective pressure to do so. i mean, think toilet tank design, not sports car.

#50188: — 11/22  at  05:09 AM
ekzept,

Of course there IS optimization in evolution. It is going on all the time with all the organisms. I am sure the that line of squid is optimized to survive and reproduce in its niche or in the way to become so.

Of course there is selective presure for squid mobility. That pressure caused the squid to develope mobility in the first place, and then to improve it to quite a respectable performance. Punctured or squalid squids are more likely to become seafood, I presume.

There must an answer why squids did not discover a more efficient way of getting around in water, like fish or sea serpents. Maybe potential squid predators are wired for discovering the fishlike movements of fish, and are unable to identify as seafood a multi-legged balloon with an orifice jetting out seawater.

#50227: Keith Douglas — 11/22  at  09:47 AM
Several people have told me that an obstactle to developing new areas of science is "math inertia" - the idea that you should learn only areas of math that were useful in the past to your particular field. (This is particularly true in psychology and social sciences, where statistics and maybe a some calculus are used and not much else.) It has been my experience that the computing people have been the most open to learning weird new branches of math. (For instance, they seem to have found a home for a lot of those weird logics that philosophers keep inventing. )

#50241: — 11/22  at  11:17 AM
I wish to change my hypothesis of why squids never developed fins like fish (Comment 50188 above). For effective muscle action, a solid framework or skeleton is required, which squids dont have.

If I had to design a system for moving around in water having a soft tissue body, the pulsating baloon design is not so crazy. I would make an inflow orifice at the forward side and use a diaphragm pump design to force the water out at the back end.

Having a workable prototype, I would proceed to divide the pump into several independent pumps connected in series and/or parallel, and install effective valves, all coordinated by a central processor.

The fortunate crittle possessing such a system would be produce a continuous jet of high pressure water.

Ah, I was born to be an Intelligent Designer!

#50242: — 11/22  at  11:18 AM
I wish to change my hypothesis of why squids never developed fins like fish (Comment 50188 above). For effective muscle action, a solid framework or skeleton is required, which squids dont have.

If I had to design a system for moving around in water having a soft tissue body, the pulsating baloon design is not so crazy. I would make an inflow orifice at the forward side and use a diaphragm pump design to force the water out at the back end.

Having a workable prototype, I would proceed to divide the pump into several independent pumps connected in series and/or parallel, and install effective valves, all coordinated by a central processor.

The fortunate crittle possessing such a system would produce a continuous jet of high pressure water.

Ah, I was born to be an Intelligent Designer!

#50280: — 11/22  at  01:19 PM
It's not exactly rocket science.

Seriously, this is a good example of the lay person's predicament. A Dr Myers may not understand the details, but he'd be comfortable with the layout, assured by the peer review process, will know from experience of publication that knowledgeable and helpful people exist who are always delighted to point out any errors, and probably confident that if he could only find the time for
a bit more background reading he could pick up enough to make sense of the more techie bits. Next year, maybe.

A lay person has none of these things. Popular science books don't always help, although some can. I was lucky to given a copy of Buchsbaum's "animals without backbones" as a young child and was captivated. Although I've studied no
biology beyond basic schooling the richness and the sheer clutter of the subject has always made it seem the most interesting of the sciences. Distance lending enchantment maybe. But what is one to make of "A brief history of time", say? There's no sense of depth there - no bibliography, not even suggestions for further reading. It's no more than a "trust me, I'm a scientist".

So on what basis can someone with no technical background identify false science, with nothing else to go on? Take Graham Hancock's books - they're an easy read, quote lots of authoritative-sounding sources which might or might not exist, link in nicely with Cthulhu and if it's all
garbage, well maybe Dr Hawking's book is garbage too (let's not go there just now), and all the rest.

This is (evidently) a rant and I'm not offering any solutions, except to say that Dr Myers is providing an invaluable service through the fascinating science papers (like this one) he collects and publishes here, that
illustrate the depth of the subject. ID, from what I've read of it, seems fundamentally shallow and to exist so far only as a fruitless parasite on evolution, having added no value to date. But how to get this across in a culture that seems to see "de-cluttering" as a virtue and
simplicity as attractive? Astrology, alternative medicine, false science are simple, soft and comfortable escapes from reality. Anyone can understand them, for there's nothing to understand. Reality is hard; science is hard. There's no comfort there.

#50289: ekzept — 11/22  at  01:43 PM

Anyone can understand them, for there's nothing to understand. Reality is hard; science is hard. There's no comfort there.

yeah, especially when kids -- and grownups -- are content with what is laughably called a literature search these days. i don't think most adults have visited a library since they were in school.

and in my experience high schools don't help. seems to me they're more concerned with getting literature citations perfect in bibliographies than teaching kids how to dig for stuff.

and most community libraries show the wear and lack of interest, too.

#50310: — 11/22  at  03:29 PM
From the author:

Wow. My work hardly generated this much interest from my advisor! I'm currently beating out Paris Hilton and McCain for comments. Only Darwin has me beat. Keep it going. I need a job.

Look, I can't answer all these questions right now, but I will say that I wrote this paper to people in my field. I am impressed that there are others outside the field who are interested. So on my way home last night, thinking about all you people blogging about my paper (an honor second only to having some Paris artist write a corny epic poem about ones work--see the early pages of the journal), I decided I will try to pen a version of the paper for a more general audience. I'll let you all know where I send it. And I'll do my best to include cool animations

But the point of the paper was this. Squid squirt, they don't puff. And given what they have to work with and what their niche is this appears to be the best way to propel themselves for reasons of both efficiency and survival. The larger point of the paper is that what is found to be efficient in an engineering lab is not necessarily used in nature, and we engineers need to be careful about thinking that way about biology. Ok, it is alright to have hypotheses, but these vortex-rings-in-squid hypotheses were hardly or not even being tested. Rather, they were simply reinforced by earlier assumptions of vortex ring propulsion in squid.

My beef is against story and celebrity science. Everybody wants a cool story. Sharkskin bathing suits, giant squid, nanobots, and the like. To most, my two most significant findings as a scientist so far have been downright boring: squid don't use pretty, highly efficient smoke rings, they just squirt, and fish don't have any amazing drag reducing ability, the drag is basically what you would expect for a vehicle of their size and speed. See, to me it isn't about the story. The story has already been written. The truth is what it is. My job is to figure out what is actually going on. To me, that is a cool and awesome responsibility.

Hey, there's nothing wrong with thinking a particular finding is cool because it really is very fantastically cool, but the true appreciators of science are those who find the truths (i.e. strongly supported theories) of the natural world marvelous, no matter how mundune they might seem.

Ironically, in the squid work, this approach of mine, to simply let the biology speak for itself, led us to discover that vortex ring formation is greatly impacted by background flow past the jet nozzle and the result is that squirt-like propulsion likely makes it possible for squid to swim more efficiently. So after all the let down regarding vortex rings we uncover a hidden truth. Wow.

#50312: PZ Myers — 11/22  at  03:41 PM
Squirt vs. puff is a story...there's no reason a well-told story can't also lead us to a piece of the truth.

Hey, please do write a general-audience version of the story. If you can't get it published in an official journal, I'd be honored to include it here.

#50398: — 11/23  at  06:42 AM
We engineers should look at natural critters doing their things like those squids propulsing themselves by intermittent squirt, and ask ourselves why they are doing what they are doing and not something different or in a different way. In case we see the poor animals behaving in an apparently inefficient way, we should look for additional factors and try to explain it.

I think the descriptive aspect is very important, but we should not satisfy ourselves with describing reality, we should think about function and evolution. That was what Darwin did, describing and trying to explain how the things he discovered came about.

For example, the squid technique of self propulsion seems to me improvable. I presume velocity and agility is important for the squid. However, it seems to be optimal for the squid. Why?

Also, as former swimmer and father of 4 competition swimming girls, your comment on drag interests me. They are selling (and I am buying) all kind of cool swimming suits purportedly copied from fish, that reduce the swimmers drag. What is your opinion?

#50466: — 11/23  at  02:59 PM
I started out as an engineer, but have no knowledge of hydrodynamics.

In my experince what you learn is how to make do with some of the simplifying models that the paper exemplified, and how to make orders of magnitude calculations to quickly throw out bad models or errors. So you don't go for complex math but try to make it as simple as possible.

As the author, I found the hidden truth on background flow the most educational find of the paper.

#50618: ekzept — 11/24  at  03:59 PM
more on the biomechanics of swimming, this time in the small, at my blog.