Acoustic radiation of inlet-turbulence/rotor interaction in free and ducted spaces
Abstract
The far-field acoustic radiation caused by the inlet-turbulence/fan-rotor interaction in free and ducted spaces is studied theoretically, discussing the computational economy and the aerodynamic response function parameters. The incompressible, two-dimensional unsteady thin-airfoil theory is combined with an acoustic radiation model of concentrated point dipoles. The study shows that the far-field power spectral density of the associated sound is largely affected by the nature of the incoming turbulence, especially the circumferential correlation scale. With circumferentially non-correlated inlet-turbulence, the associated spectrum has harmonics of the rotational frequency of the rotor, whereas well-correlated turbulence makes harmonics of the blade passing frequency. Finally, the duct termination has a considerable effect upon the acoustic radiation of sound generated inside a duct, especially at frequencies below and close to the cut-off frequency.
- Publication:
-
Tokyo University Institute of Space and Aeronautical Science Report
- Pub Date:
- January 1981
- Bibcode:
- 1981TUASR..46....1K
- Keywords:
-
- Inlet Flow;
- Noise Generators;
- Rotors;
- Sound Waves;
- Turbulent Flow;
- Acoustic Ducts;
- Far Fields;
- Green'S Functions;
- Power Spectra;
- Random Loads;
- Sound Pressure;
- Acoustics