Wind tunnel test of Japanese arrows with the JAXA 60-cm magnetic suspension and balance system

Abstract

In order to understand the aerodynamic properties of Japanese arrows, several types of shafts without fletching and various types of Japanese arrows were examined in a low-speed wind tunnel equipped with the JAXA 60-cm magnetic suspension and balance system. The main component of drag acting on the shaft is viscous drag from the boundary layer. This viscous drag can be evaluated analytically. A simple new method to estimate the effects of fletching on the lift of the arrow was proposed in which we found that lift is proportional to the angle of attack of the arrow but not to the rotation speed or angle. Time history results for the lift on rotating arrows in the magnetic suspension and balance system indicate that this method effectively estimates the lift on an actual rotating arrow in flight. The lift and pitching moment were mainly generated by fletching, and the drag from the fletching was similar in magnitude to that of the arrow shaft. For Japanese bamboo arrows tested with a field point, the drag, lift, and pitching moment coefficients were evaluated to be in the ranges of 3.5–3.7, 0.4–0.8, and −0.15 to −0.25, respectively, at Reynolds numbers of an arrow in flight.