空力音の発生機構に関する実験解析 : 第1報,円柱表面圧力変動の空間構造について

抄録

Spanwise coherent structure of surface pressure fluctuation on a circular cylinder is studied experimentally in order to obtain quantitative information for understanding the generation mechanism of aerodynamic sound from the cylinder at Reynolds numbers between 5 × 10³ and 1.4 × 10⁵. Spanwise distribution of the coherence function between surface pressures is kept as high as up to several diameters for the frequency components of the so-called orderly structure, or the Karman vortex shedding frequency and its harmonics, while the coherence function for the turbulent frequency component decays rapidly spanwise to half-diameter. Spanwise coherence function of the surface pressure is calculated as an exponential function of spanwise spacing and Reynolds number. The correlation length of the flow structure is found to be inversely proportional to Re^1/2.