空力音の発生機構に関する実験解析 : 第2報, 表面圧力変動と空力音の相互相関について

抄録

The mechanism of aerodynamic sound generation from a circular cylinder is investigated experimentally using coherence functions between surface pressure fluctuation and radiated sound at Reynolds numbers from 10⁴ to 1.4×10⁵. The correlation between the surface pressure fluctuation and the radiated sound at the fundamental frequency is good, indicating the strong contribution of ordered structures to aerodynamic sound generation. The characteristic length of ordered structure L_c is estimated using the integral scale of the spanwise coherence function of surface pressure fluctuations. The sound pressure is calculated using a modified Curle's equation, with the characteristic length and measured surface pressure fluctuations. The predicted spectra of radiated sound are in good agreement with those actually measured up to five times the fundamental frequency. This result shows that L_C is useful for estimating the character of radiated sound from a circular cylinder.