121 Aerodynamic specification and flow visualization on disk wheel which produces forward lift

Abstract

In recent years, bicycles are attracted as lower environmental burden transfer. Then, amateur competitors keep increasing, and they began to indicate data of aerodynamic specification of bicycle components as frames, spokes, helmets and wheels. This study verified the effects of Sub9 produced by Zipp. Zipp argues this wheel "produce forward lift" in a wind angle of 12 to 18 degrees. Therefore, we made 3 kinds of wheels, plain disk, normal disk wheel and Sub9 model. Those were used as a drag force measurement and flow visualization, and investigated in non-rotate conditions and rotate conditions. Drag force of each model was measured with three components load cell. Flow visualization in a smoke wind tunnel was also carried out in a vertical plane. As a result, Sub9 produced little thrust over wind angle of 16 degrees. Plain disk have similar specification to Sub9, and normal disk wheel is the worst wheel in this study. The results of the flow visualization also explain these phenomena well.