What is the most aerodynamic form?

[mathen]

I was always taught that a teardrop was, giving teh perfect boundary layer etc. If this is teh case, why have I recently been informed that a free falling water droplet remains spherical in shape? (Ref: intellectual quix QI with Stephen Fry).

[kempie]

It was shown by Pruppacher and Beard and by Pruppacher and Pitter that drops of water with radii <500 μ approximate to a spherical shape; larger drops are deformed into oblate spheroids, which with increasing size develop a flattened base and subsequently a concave depression.

Although the teardrop is a more aerodynamic shape than a sphere it does not follow that falling spheres will turn into teardrops; a tennis ball certainly doesn't and neither does a drop of water. This is because the drop retains as close to its spherical shape as possible through surface tension.

[pawwaw17]

as far as the most aerodynamic form was a bean shape, an oval squezed either side, i think this is correct.