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posted by cmn32480 on Monday June 12 2017, @04:03PM   Printer-friendly
from the row-row-row-your-bot dept.

An article in Physics Today delved into the question of which would be faster: rowing in phase with all of your teammates, or rowing out-of-phase:

Rowing is a challenging sport, and not just for athletes. It mixes physiology, mechanics, and fluid dynamics, so from a physicist's perspective, the sport is much more complex than the elegant movement of a rowing shell might suggest.

Many scientists have tried to work out the details of rowing propulsion, often with a view to improving the performance of rowing crews. For example, in a 1971 Science paper (volume 173, page 349), Thomas McMahon showed that the speed of a racing boat scales as the number of rowers to the power 1/9. In our research, we have taken a closer look at the boat speed within one rowing cycle. In a single stroke, a propulsive phase is followed by a gliding phase. As the figure shows, for racing boats, the variation in speed during the stroke is typically around 20% of the mean speed of 5 m/s or so. Such a variation is a consequence of the synchronized rowing of the crew, a technique that seems to be essential for success in top-level rowing competitions. Consider, however, that for a boat moving through water, larger fluctuations about the boat's average speed imply increased friction on the hull. As a consequence, the mean power dissipated due to fluid friction for speed variations typical of a racing boat is about 5% higher than it would be if the boat could somehow be propelled steadily at the same mean speed.

The investigators suspected that reducing the variation in speed would result in less friction and a higher average speed. To test this, they created a 'bot boat' where they could programmatically control the phase at which each mechanical rower placed their oars into the water — anywhere from 0 to 45° out of phase. Initial results showed that out-of-phase rowing was smoother. Yay! But the boat was slower! Why?

Supplement: The great row bot race

In rowing races, a crew's synchronized motion forcefully propels the rowing shell forward. But the jerky motion of the boat creates a lot of friction on the hull. Can the crew gain an advantage by rowing out of sync? The video shows two trials conducted at the École Polytechnique in Paris using a 1/10-scale boat and robot rowers. In the top panel each robot rows 45° out of phase with its neighbor. In the bottom panel the row bots simulate conventional synchronized rowing. The asynchronous rowing is smoother, but in this case, slow and steady loses the race.

Download Original Video (7.1 MB)

An old adage humorously suggested that "Scientists frequently find that a week in the library can save an hour in the lab." What experiments have you been involved in where the results were counter to your expectations?


Original Submission

 
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  • (Score: 5, Funny) by ikanreed on Monday June 12 2017, @05:39PM (3 children)

    by ikanreed (3164) Subscriber Badge on Monday June 12 2017, @05:39PM (#524523) Journal

    An American engineering firm and a Japanese engineering firm decide to have a rowing race.

    The Japanese firm enters a team with 4 rowers and a navigator.
    The American firm enters a team with 3 rowers, a head navigator, and a middle navigator to take some of the burden off the head navigator, who obviously had a very important job.

    The race takes off, and in spite of a serious effort by the American team, and a small head start, the Japanese team wins the day. This puzzles the American team who had be regularly beating every other American company they had been facing off against. They decide they urgently need to address the issue before next week's rematch. They decide to get an analyst to observe their rowers. The navigators take rower #3 off the boat to make room for the analyst.

    The next race is even worse for the American team, they're left in the dust. However, the analyst gets some very good notes, and the navigators decide he was a very good idea to have along. His conclusions are that while the rowers are good at their jobs, they're not as motivated as they could be, and more training could help them. Not wanting to give their rowers a race off for training, and seeing that the notes indicate that rower #2 needs more training than #1, they fire #2 and and get a in-race training export to motivate their rowing team during the next race.

    Rower #1 puts in an amazing effort, and actually burns out every muscle in his body trying to keep up with the Japanese team, though failing in the end. This success earns the in race trainer praise for his good work, the analyst gets a medal for correctly identifying the problem, the middle navigator gets a new title(upper-middle navigator) for his leadership, and the head navigator takes a well-earned nap.

    Rower #1 is sensibly fired for not winning the race.

    Starting Score:    1  point
    Moderation   +4  
       Insightful=1, Informative=1, Funny=2, Total=4
    Extra 'Funny' Modifier   0  
    Karma-Bonus Modifier   +1  

    Total Score:   5  
  • (Score: 2) by Geezer on Monday June 12 2017, @05:44PM

    by Geezer (511) on Monday June 12 2017, @05:44PM (#524527)

    "If the horse isn't fast enough, it needs more jockeys."

  • (Score: 2, Insightful) by Anonymous Coward on Monday June 12 2017, @06:29PM (1 child)

    by Anonymous Coward on Monday June 12 2017, @06:29PM (#524570)

    That reminds me of the story of seven dwarfs I've once read on the net. From what I remember, it went about like this:

    Once upon a time, seven dwarfs were working in the ore mines, and they were happy, their work gave them enough income and everything was good.

    One day, they noticed that they didn't know how much ore each of them mined. After all, maybe one of them was slacking at the expense of all the others? So they decided that one of them should watch the amount each of them mined. Of course that dwarf wouldn't have time to mine himself. They called that dwarf "controller". The controller then looked at the work of the others, and now they knew exactly how much ore each of them had mined.

    However they noticed that for some unknown reason their total output was now lower. They decided that they needed more motivation for their hard work, so they decided another of them should work as motivator. Of course that also was a full-time job, and thus that dwarf also wouldn't mine.

    But the dwarfs found out that despite of the motivator, their output was not growing; indeed, it went down even more. They look at the situation and decide that it must be because their work is not sufficiently coordinated: Everyone is working basically on his own. So they decide they need someone who coordinates their work. They call him the manager, and of course he doesn't mine himself any longer, too.

    But somehow this didn't help either; the output was going down again. So they decided that someone had to look at the mining process, to detect and find any problems with it. That dwarf was called the process manager, and also did no longer mine himself.

    But this still didn't help, the output went down further. Moreover, due to the bad situation, there often happened disputed among the dwarfs. So they decided that probably those disputes were responsible for the further down trend, and they designated another dwarf as professional mediator of disputes. Of course that dwarf no longer mined, either.

    But still, the output was reduced further. They figured it had to be because with all those different rules, things had become complicated, and it wasn't always clear who was responsible for what. So they decided they needed someone who would know who was responsible for what, and who would make sure that the right people were approached with each problem. They called him business administrator, and of course he didn't have any more time to mine.

    So the end result was that only one dwarf was left mining.

    • (Score: 2) by Jerry Smith on Tuesday June 13 2017, @09:42AM

      by Jerry Smith (379) on Tuesday June 13 2017, @09:42AM (#524839) Journal

      I borrowed this for class, thank you for reminding me it existed!

      --
      All those moments will be lost in time, like tears in rain. Time to die.