Jet Noise : 2nd Report, Effect of Shear on the Noise of a Jet

抄録

Considering the structure of turbulence in the mixing region of jets where the noise is mostly generated, the influence of the exit velocity profile (shear) on the jet-noise has been studied with the following results. Weakening 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 to the fourth power in the lower side. Total intensity of the noise varies with about the third 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 weakening the strength of shear.