Kazumasa Okubo

Fundamental Study on the Efficiency of Power Generation System by Use of the Flutter Instability

Recently, Isogai et al.[1] proposed a new idea on power generation by use of flutter instability of thin airfoil. The heaving steady oscillation, which produces the electrical power from wind energy, can be excited by the forced torsional oscillation initially given to the heaving and torsional 2DOF system at any wind velocity ranges in his study. On the other hand, the authors have investigated the coupled flutter mechanism of various bluff bodies from the point of two different torsional and heaving branches by use of the “Step-by-Step flutter analysis method” (abbreviated by the SBS method).[2,3,4] Isogai’s idea is identical to the heaving branch flutter in the SBS method. Thus, the improvement of the power generation performance is investigated in this paper basing upon the flutter mechanism, and the efficiency of power generation by use of the heaving branch flutter was compared with that by the torsional branch flutter. It has been clarified that the obtained energy by the heaving oscillation would be larger than the supplied energy for giving initial torsional oscillation to the system and loss-energy caused by the structural damping and the aerodynamic damping over certain wind velocity range.Copyright

STUDY ON MECHANISM OF SEPARATION INTERFERENCE METHOD TO REDUCE AERODYNAMIC RESPONSE OF SQUARE PRISM

完全剥離型断面である正方形断面角柱を対象として，久保らが提案している剥離干渉法（Separation Interference Method）の空力的な耐風安定化の手法について，各種風洞実験から空力安定化に寄与するメカニズムの解明に関する検討を行った．その結果，剥離干渉法が有効に機能するためには，剥離点間で生じる循環流が重要な働きをしており，循環流によって生じる圧力分布の変化によって空力安定性の優劣が決定することを明らかにした．また，剥離干渉法が有効に機能している場合には剥離干渉後の流れは気流迎角の影響を受けにくいことを示した．