Aerodynamic Characteristics of Busemann Biplane by Wake Measurements in Low-Speed Wind Tunnel

Abstract

In this study, the basic aerodynamic characteristics of a Busemann biplane model in a low-speed wind tunnel were clarified by the wake survey technique. A low-speed wind tunnel of the blowdown type was used, and it had an exit nozzle size is in 1.5 m © 1.5 m. A wake measurement system and six-component balance system were installed in the test section. A five-hole probe was used in the wake measurement system to measure the velocity distribution. The Busemann biplane model was designed to cruise at Mach 1.7. The total length of the model was 742 mm, and the width was 556 mm. The shape of the fuselage was 76 mm square on a side, and the nose had a double-conical shape. The flow velocity was 20 m/s, and the Reynolds number derived from the mean chord length was 1.4 © 10 5 . The results of the study are summarized as follows. Based on the visualization of the wake flow, vortices were generated from the tips of the upper and lower wing elements of the biplane at an attack angle of ¡ = 0°, but the vortices had an opposing rotation direction. Analysis of the wake data showed that locally induced drag was not generated at the wing tip. At ¡ = 6°and 8°, the profile drag increased, probably due to the influence of the flow separation from the upper surface of the upper wing element. However, the total lift coefficient increased with an increasing angle of attack, even at ¡ > 8°. Therefore, it can be concluded that the biplane lift is mainly generated by the lower wing elements.