Development of a New Method for Reducing Impulsive Aerodynamic Noise by means of Active Control Method

点击翻译按钮获取中文摘要

(1) Numerical and aerodynamic analyzes were carried out on the emission of a propagating compression wave from an open end of a constant area tube. The generation mechanism of an impulsive wave from the open end was charified and the effects of various factors on the magnitude of the inpulsive wave were indicated.(2) The experiment on the impulsive wave generated by the emission of a compression wave and a shock wave from an open end of constant area tube was carried out. The results agree well with the numerical results mentioned above. It is shown that the boundry between the near field and the far field is about one diameter downstream of the open end of the tube.(3) In order to do active noise cancellation of a positive impulsive noise by adding an inverse wave, a negative impulsive wave generator was designed and constructed. This device utilizes unsteady mass efflux by an unsteady expansion wave of a shock tube.(4) The strength of the negative impulsive wave generated by the above device depends only on the maximun time rate of pressure change of the expansion wave at the shock tube exit. The relationship between the unsteady mass efflux and the negative impulsive wave was obtained.(5) The effects of various types of silencers on an impulsive noise emitted from an open end of a shock tube was investigated numerically and experimentally, and the design factors of the silencer reducing impulsive aerodynamic noise were suggested.