239 Measurements of Flight Characteristics of Turbo-Javs

Abstract

The "turbo-jav" which is used for the javelic throw in the junior Olympic games has four fins at its tail unlike a spear used for the javelin throw. In order to investigate the aerodynamic characteristics of the turbo-jav, we performed wind tunnel tests, throwing experiments and numerical simulations for the flight of the turbo-jav. In the wind tunnel test, we measured the drag force, lift force and pitching moment acting on the turbo-javs in a low speed wind tunnel at the flow speed up to 25 m/s. The experimental results showed that these aerodynamic coefficients are almost constant irrespective of the Reynolds number for given angles of attack when the flow speed is larger than about 12.5 m/s. The moment coefficient was found to decrease from zero with increasing angle of attack from zero. In accord with this property for the pitching moment, throwing experiments showed that the turbo-javs fly stably with oscillating angle of attack around 0. The flying distance, the orbit and the variation of angle of attack for turbo-javs launched by a launcher agree closely with the numerical simulation performed based on the wind tunnel test. The turbo-javs launched by the launcher are found to fly without rolling whereas the turbo-javs thrown by athletes rotate considerably. A comparison of the throwing experiments by athletes with those by the launcher suggested that the turbo-javs flying without rolling could reach farther than turbo-javs with rolling for the same initial conditions.