Yasufumi Konishi

Introduction of 1-m MSBS in Tohoku University, New Device for Aerodynamics Measurements of the Sports Equipment

Support interference in wind tunnel testing is an unavoidable effect. It is difficult to measure the aerodynamic force acting on a model such as a ball owing to this effect [1]. A magnetic suspension and balance system (MSBS) suspends the model without any mechanical supports by using magnetic force, and at the same time, can measure the aerodynamic force acting on the model. The 1-m MSBS, located at the Institute of Fluid Science, Tohoku University, is the world’s largest MSBS. It has a 1-m-wide octagonal cross section. A sphere is taken as the experimental object, and the results of the aerodynamic force acting on it are presented. The diameter of the sphere is 150 mm, and its blockage ratio is 2.1%. The experiment was conducted at Reynolds numbers ranging from 0.5 × 105 to 4.7 × 105. It clearly shows the drag crisis at approximately Re = 3.7 × 105, and the fluctuation of the sphere abruptly increase around this region.

Effect of Camber on Badminton Shuttlecock

In this study, we conducted experimental measurements and computational analysis to investigate the aerodynamics of a shuttlecock, especially the effects of the camber of the shuttle’s skirt. The static aerodynamic coefficient from the experiment showed that the camber of the skirt was able to modify the aerodynamic characteristics. A positive camber, which indicates bending the blade toward the outside, causes a slight increase in lift and a decrease in drag. On the other hand, a negative camber causes an increase in drag, and an insensitive region in the lift and a pitching coefficient of approximately 0° was observed. This result leads to instability in the flight of the shuttlecock. The pressure distribution calculated using computational fluid dynamics revealed that each blade functions as a two-dimensional airfoil. However, in most cases, the blade is in stall condition due to an initial divergence angle of the skirt.