ジェット騒音 : 第2報, シヤーの騒音強さに対する影響

抄録

Considering the structure of turbulence in the mixing region of jets where the noise is mostly generated, the influences of the exit velocity profile (shear) on the jet-noise have been studied and the following are results. Weaking the strength of shear makes the spectrum of the noise source per unit volume shift towards the lower frequency side. The spectrum of the noise as a whole is proportional to the second power of the shear strength in the higher frequency side and the fourth power in the lower side. Total intensity of the noise varies with about the fourth power of the shear strength as long as the mixing layer contributes effectively to the noise generation. When it ceases to play such a role, the relation obtained is not always satisfied to show the limit of noise attenuation by means of weaking shear.