Unsteady Rotor Aerodynamics and Acoustics

Abstract

An aeroacoustic method for noise prediction of helicopter rotors in forward flight is presented. The unsteady aerodynamic flow field is computed using an Euler solver for arbitrary moving coordinate systems and flexible grids taking into account the prescribed rigid blade motion. Using the computed pressure data as input, two acousticmethods are applied, on one side the linear part of the acoustic analogy method and on the other side the Kirchhoff method. First for the 4-bladed ONERA/ECF 7AD rotor in high-speed forward flight ( &#61 0.4) the blade pressure data computed with the present method is compared with experimental data and numerical results of other authors e.g. Chimera method. A good overall agreement can be stated. For the same ONERA/ECF 7AD rotor test conditions defined in the HELISHAPE project are applied ( &#61 0.33). The comparison of computed pressure data with the experimental data is less.