Generation of noise by turbulence
Abstract
The notion of noise source is elaborated, distinguishing between turbulent agitation, which is a cause, and acoustic agitation which is a minor effect or subproduct whose essential particularity is its propagation at the speed of sound. This allows for a precise definition of noise, derived from acoustic potential and apart from pseudo-noise linked to turbulence. The equation, valid for this potential, is established by an almost complete elimination of state variables and is linearized. This enables a study of convection and refraction effects and shows that generated noise is in proportion to the density relative variation rate. A model of anisotropic turbulence inside a shear flow is proposed. Its use shows that the noise generated inside a vortex tube is proportional to the square of the circulation. Application of the findings to interpretation of noise measurements in wind tunnels, e.g. aircraft noise predictions, is discussed. An extension of the method in order to include noise near obstacles is outlined.
- Publication:
-
Unknown
- Pub Date:
- 1981
- Bibcode:
- 1981gnt..rept.....L
- Keywords:
-
- Noise (Sound);
- Noise Generators;
- Potential Theory;
- Turbulence;
- Acoustic Propagation;
- Aircraft Noise;
- Hilsch Tubes;
- Shear Layers;
- Vortices;
- Wind Tunnel Calibration;
- Acoustics