Measurement of Aerodynamic Forces near Critical Reynolds Number Acting on a Rotating Sphere

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K17851
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 59020:Sports sciences-related
• Research Institution: Tohoku University
• Principal Investigator: Okuizumi Hiroyuki 東北大学, 流体科学研究所, 技術専門職員 (60647957)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 回転球 / マグナス効果 / 負のマグナス効果 / 支持干渉 / 磁力支持天秤装置

Outline of Final Research Achievements

The objective was to clarify the aerodynamic characteristics of a rotating sphere with dimples on the surface using the 1-m magnetic suspension and balance system (1-m MSBS) at the Institute of Fluid Science, Tohoku University.
A magnetic suspension and balance system is an effective way to avoid support interference in wind tunnel testing.
I made it possible with magnetic levitation of the rotating sphere by improving the position sensor system. And I adopted air-jet nozzles to rotate the sphere model suspended magnetically. Applying this method, a wind tunnel test was conducted at the wind speed of 7m/s (Reynolds number = 6.5 × 10^4) and rotational speed within 600 rpm. An occurrence of the drag crisis was confirmed, and drastically decreasing the Magnus force was also measured.

Free Research Field

実験流体力学

Academic Significance and Societal Importance of the Research Achievements

磁力支持天秤装置による回転球の空力試験技術を開発したことで、今までほとんど例のなかった、支持干渉のない真の回転球の空力特性を調査する環境が整った。最初の風洞試験では、回転する球模型に働く空気抵抗やマグナス力が、その回転数の変化に伴って劇的に変化する様子を捉えた。今後この技術を用いることで、回転球の空力現象解明や、スポーツ分野でよく目にするディンプル状やシーム状の表面性状をもつ球状物体の回転時の空力特性解明が期待される。また、本技術を発展させ、球から形状が大きく異なる強風災害の飛散物形状である角柱などにも応用を広げることで近年増加する強風被害対策にも貢献できる。