The Longest Now

Lovely images (though not terribly informative), good review.

I’m not sure how serious a flaw it is to use the Strouhal number to characterize effiiciency, but at first glance it seems the wrong quantity.  A good measure of efficiency should involve the volume of liquid moved, or better yet the work done in a typical stroke (integrating the momentum imparted to the liquid over the stroke duration), not just the amplitude and frequency of strokes used.  No surprise that the Str. number range is different for large birds than for small ones.

Awesome, flawed overview of Strouhal Number …