2023-11-06 ブラウン大学
◆研究により、柔軟な材料が適切に選ばれ、適切に設計される場合、衝撃を和らげるのに役立つことが示されました。しかし、柔軟性が過度である場合、逆に最大の衝撃力を増大させる可能性があることも明らかになりました。したがって、腹打ち飛び込みの痛みを軽減するためには、適切な材料と設計が重要であり、柔軟な材料が衝撃を吸収し、振動を増幅しないように選択すべきです。
＜関連情報＞
- https://www.brown.edu/news/2023-11-06/belly-flop-mechanics
- https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/slamming-forces-during-water-entry-of-a-simple-harmonic-oscillator/4E80C056B7CF95B96714AB11BDF938DF
単純調和振動子の入水時の衝撃力 Slamming forces during water entry of a simple harmonic oscillator
John T. Antolik,,Jesse L. Belden,Nathan B. Speirs[ and Daniel M. Harris
Journal of Fluid Mechanics Published:06 November 2023
DOI:https://doi.org/10.1017/jfm.2023.820
Abstract
When a blunt body impacts an air–water interface, large hydrodynamic forces often arise, a phenomenon many of us have unfortunately experienced in a failed dive or ‘belly flop’. Beyond assessing risk to biological divers, an understanding and methods for remediation of such slamming forces are critical to the design of numerous engineered naval and aerospace structures. Herein we systematically investigate the role of impactor elasticity on the resultant structural loads in perhaps the simplest possible scenario: the water entry of a simple harmonic oscillator. Contrary to conventional intuition, we find that ‘softening’ the impactor does not always reduce the peak impact force, but may also increase the force as compared with a fully rigid counterpart. Through our combined experimental and theoretical investigation, we demonstrate that the transition from force reduction to force amplification is delineated by a critical ‘hydroelastic’ factor that relates the hydrodynamic and elastic time scales of the problem.
