Aerodynamic characteristics of the turbo-jav and its flight trajectories

Abstract

The “turbo-jav” which is used for the javelic throw in the junior Olympic games has many characteristic features in geomety different from a spear, including the presence of tail fins. In order to investigate the aerodynamic characteristics of the turbo-jav, we performed wind tunnel tests at the flow speed up to 25 m/s for various angles of attack to measure the drag force, lift force and pitching moment exerted on the turbo-jav. Using the aerodynamic coeffients obtained, we numerically calculated the flight orbit of the turbo-jav and the variation of the angle of attack, starting from the initial condition obtained at throwing experimens. The flyng distance predicted by the numerical simulation was found to be much shorter than that obtained at the corresponding experiments. Since the amplitude of the oscillation in angle of attack during the flight was much larger in the numerical simulation compared to that in the experiment, we proposed a new model in which the resistant term proportinal to the square of the angular velocity was added to the pitching moment. The simulation result was discussed in relation to the oscillatory behavior of the turbo-jav.