Breakthrough Swimming
by Cecil Colwin

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Book Reviews of Breakthrough Swimming

Book Review: Dangerously wrong with Fluid Dynamics
Summary: 1 Stars

The author did correctly state, that water is not the same as air: ie. water being approx 800 times denser. But, he then tries to see comparisons between aerodynamics and hydrodynamics. The ideas cannot just be directly transferred:

1. Hand like Aerofoil - Your hand is really a very bad aerofoil shape, try and find any aircraft with an aerofoil that is as dumpy as your hand (thickness to chord). Also, in swimming your hands are moving back through the water to propel you forwards, and if you stroke count and measure your stroke length on dry land you find that at your optimum efficiency your hand position is creeping slightly before where you put it in. Your hand is nearly static and your body is travelling forward.

2. Magnus effect: a rotating cylinder can produce lift - The speed of rotation needs to be quite great to achieve the desired result and what part of your body are you wanting to produce lift from?

3. Alula effect; like a leading edge slot on an aerofoil - How many times its not air your swimming through. Water is a lot denser and is hard to compress, you're not going to have any separation and apart from that read the 'hand like aerofoil' assumption.

4. Lunate Shapes: like the crescent shape of a swifts wings to lessen induced drag - He compares that if you can bend your hand and arm to a crescent shape it will lessen drag. However, the swift?s wings are a thin aerofoil section your hand and arm are not.

5. Vortex Analysis- seeing bubble trails to study efficiency- this is the only part of the fluid dynamics part that actually was a little interesting, although science is mainly about interpretation of results, which I think was again misguided or not clearly explained. The most efficient generation of vortex would be to only generate one and keep that vortex on your hand, as generating a new vortex wastes a lot of energy.

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