Timeline for Sea creature moving via rotational motions
Current License: CC BY-SA 3.0
7 events
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| Apr 13, 2017 at 12:52 | history | edited | CommunityBot |
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| May 2, 2015 at 2:07 | comment | added | Hugh Allen | Even if you ignore variations in speed, most swimming strokes are not what Purcell calls "reciprocal motion". He refers to it as "One special kind of swimming motion" - not the only kind, and not even the most popular kind. So your statement that "Swimming strokes are symmetric if the time is reversed" is false. It is only sort of true for the scallop, which has a particularly simple shape - two rigid pieces held together by one hinge. | |
| May 1, 2015 at 18:16 | history | edited | Bosoneando | CC BY-SA 3.0 |
corrected spelling (Reynold -> Reynolds)
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| May 1, 2015 at 18:15 | comment | added | Bosoneando | @HughAllen Having no inertia implies that, for net motion, is irrelevant: if you eliminate inertial terms from the Navier-Stokes equation, it doesn't depends on time anymore. Slower or faster doesn't matter at all. Again, I recomend you Purcell's Life at low Reynolds number | |
| Apr 28, 2015 at 15:55 | comment | added | Hugh Allen | "Swimming strokes are symmetric if the time is reversed" - this is not true in general. The scallop is a special case, and even then there is no true time reversal symmetry. One half of its swimming stroke is the opposite motion to the other, but performed much faster. If it was the same speed, the animal would indeed make no progress through the water. | |
| Apr 27, 2015 at 22:48 | review | First posts | |||
| Apr 27, 2015 at 23:01 | |||||
| Apr 27, 2015 at 22:35 | history | answered | Bosoneando | CC BY-SA 3.0 |