数値解析による流体音の音源分布の解析

抄録

This study deals numerically with the aerodynamic sound radiated from the flow over a circular cylinder at a Reynolds number of l0³. The standard acoustic analogy method is applied. The incompressible time-dependent two-dimensional flow around the cylinder is calculated by means of the finite difference method, then the variables are substituted into the approximate analytic solution of a nonhomogeneous wave equation. The result of far-field sound calculation using a solution which Howe expresses as a volume integral form is compared with that using another one which Curle expresses as a surface integral form. Good agreement is obtained between them. Howe's equation is used to investigate the sound source distribution in the flow field. The sign of the pressure fluctuation radiated from a small sound source region is opposite to those radiated from the neighboring ones. Most of the pressure fluctuations interfere and vanish as a consequence of volume integration. The remaider is observed as far-field sound. It is shown that there are some regions which contribute more significantly to the sound generation than the other regions on average in time.