Propeller/rotor sound scattered by great extension surfaces

This paper deals with propeller/rotor operating in proximity of a great ex surface, with the aim of analyzing its e ects on the emitted acoustic field. Both purely reflecting and purely absorbing surfaces are considered, and the most suitable way to model their presence is examined. To this purpose, first the e ect of the surface on the aero/hydrodynamic sources distributed over propeller and rotor blades is investigated by including it, through the mirror image method, in the aero-hydrodynamic simulation. Then, the influence of the surface on the total acoustic field is examined by assuming it as a scattering surface impinged by the pressure field radiated by the propeller/rotor. Potentialities and drawbacks of the di erent modeling approaches considered are theoretically and numerically investigated.