The wake of a duck
There’s something that’s been on my mind for over a year now. The angle of the wake of a duck moving with constant velocity in deep water is independent of the velocity of the duck (~39 degrees). Why is this? (This makes me regret not sitting in on the Part II fluid dynamics course this past term.)
According to Bertrand Le Roy:
This is because the speed of the waves depends on the wavelength in such a subtle way as to cancel the dispersion that a single wavelength wave would show.
According to Tony Zee’s 2004 ASTI lecture on back of the envelope physics, one can make a solid argument based on dimensional analysis.
Unfortunately I haven’t been able to think this one through yet, and any thoughts would be appreciated.
Filed under: Just for Fun, Physics | 5 Comments