Abstract: Ffowcs Williams/ Haw kings ( FW-H) Equation, which is directly derived from Nav ier??Stokes equations,has been the theoret ical backg round of predicting the noise gener ated by mov ing bodies. For predicting the rotornoise, in the conventio nal solution of FW-H equation, the blade is utilized as t he integr atio n surface, and complica??tion is caused when calculating the quadrupole noise. In the present work, a form of FW-H equation applied for apermeable surface was employ ed for predicting the quadrupole noise aero dynamically g ener ated by rotor bot h in hoverand forward flight. Sect ion 1 discusses the CFD calculation performed by solving the 3-D unsteady Euler's equa??tions. Section 2 describes in detail the solution of permeable??surface FW-H equation in t ime domain. The computedr esults for all cases w ere compared with ex perimental data and reasonable agr eement has been achieved. It w as alsoshow n that the dev eloped code is efficient and is capable of capturing the nonlinear quadr upole no ise for transonic ro??tor.

Key words: rotor, aeroacoustics, Ffowcs Williams/Hawkings equation, unsteady Euler’s equations