UNSTEADY LOADING NOISE OF COUNTER-ROTATING PROPELLER

The unsteady Loading noise generated by interaction of a front rotor wake with an aft rotor in a counter-rotating(CR) propeller is analyzed and the noise radiation formulae are derived. The numerical prediction of noise of a real CR propeller are completed and compared with experimental data.It is concluded that the sound pressure level (SPL) in the axial direction of the rotor is fully determined by the component of unsteady loading noise, but in rotor plane the main contribution to SPL is the component of steady loading noise and the effect of the unsteady one is limited in the range of higher harmonics in this case.