Analysis on the frequency-domain numerical method to compute the noise radiated from rotating sources

A frequency-domain solution of the Ffowcs Williams-Hawkings equation with a penetrable data surface is presented for the thickness, loading and quadrupole noise to avoid the singularities that exist in the time-domain methods. Since this method is based on the numerical integration over source time, there is no need to solve the retarded-time equation or to perform the interpolation on time-domain data, and the time-domain source information obtained by modern CFD codes can be utilized directly. The acoustic pressure spectra of monopole, dipole and quadrupole point sources in subsonic and supersonic rotation are calculated with the presented method, and the results agree well with those obtained by the retarded-time method and frequency-domain analytical method.