Dolphin Jump

Let's take a look!

Watch the video on YouTube.

What kind of experiment is this?

Experimental procedure and explanation:

• As you pursue the shape that has least drag, you eventually get to the shape of a dolphin, the so-called streamline shape.
• The important characteristic of the streamline shape is that the rear end is tapered and sharp. This avoids separation (generating a vortex), thereby minimizing resistance (drag).
• The second characteristic is that it has a round front end. This is not as important as the shape of the rear section, but rounding the front will prevent separation that could be caused by the front edge.
• You might think that a sharper front section would reduce resistance, but typically, a rounded front is better. With a sharp front end, separation could take place, depending on the angle of the flow, and resistance would increase.
• A true streamline shape is slender, but to increase buoyancy, the shape used in this experiment was not so slender.
• The target set in “Idea Contest - Playing with Flow” hosted by the Japan Society of Mechanical Engineering was to fly over a bar from a water depth of 30 cm. The highest record marked at this contest was 1.6 m from the water surface.

[Keywords]	streamline shape, resistance (fluid dynamic drag), buoyancy
[Related items]	Jump with Buoyancy 1
[Reference]	“The Wonders of Flow,” Japan Society of Mechanical Engineering, Koudansha Blue Backs, pp.148-153 and 154- 155 “Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natsume Publishing, pp. 70-71 and p. 98
[Link]	http://sc-smn.jst.go.jp/index.asp (Search for program name “Science Battle” and choose #25 Jump with Dolphin Jump!)