Broadband rotor noise predictions using a time domain approach

Abstract

This paper describes how broadband rotor noise can be predicted directly from measurements of turbulent velocity correlation functions upstream of a rotor without the need for turbulence modeling. The method is based on a time domain formulation and uses the turbulence velocity correlation function in the plane of the rotor to describe the inflow velocity statistics. The application of this theory to a rotor mounted near a hard wall is described. It is shown that rotor noise measurements are well predicted using this approach. It is also shown that to calculate the blade response correctly the time step of the numerical computation must be less than the time it takes for an acoustic wave to travel from the leading edge to the trailing edge of the blade section.