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Immersed boundary法を用いた流れ方向強制振動円柱周辺の流動解析

Flow analysis around an in-line forced oscillating circular cylinder using IB-method

木野 千晶; 渡辺 正*; 西田 明美; 武宮 博

Kino, Chiaki; Watanabe, Tadashi*; Nishida, Akemi; Takemiya, Hiroshi

流力振動現象のメカニズムに関する科学的知見を得るため、強制振動下における円柱周辺の流動解析を実施した。流体・構造連成手法としてはimmersed boundary法を用い、計算条件として換算流速において0から10の範囲を設定した。本解析を通じて、第一励振域においては、円柱後方に高圧領域が接触することから円柱に負の抗力が発生する瞬間が生じ、この負の抗力が流れ方向振動の励振力になることを示した。また、第二励振域においては時間平均された揚力が0に一致しない円柱振動条件が存在し、この現象が流れ垂直方向振動の励振力になることを示した。

Flow around an in-line forced oscillating circular cylinder was simulated numerically by using OpenFOAM in order to clarify the mechanism of flow induced vibration. Immersed boundary Method is used to solve the moving boundary. Reynolds number is set to 1000 and the reduced velocity is set to the range from 0 to 10. In the first excitation region, it is shown that negative drag force which is a factor for an in-line oscillation of a circular cylinder comes from contacting between high pressure region and a circular cylinder. The present simulation shows that twin vortex has an important role on the contact phenomena. In the second excitation region, it is shown that time averaged lift drag doesn't become zero on some oscillating conditions. It is considered that a cross-flow oscillation comes from the phenomena.

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