Acoustical Methods and Experiments for Studying Rotorcraft Fuselage Scattering

Abstract

This paper deals the activities conducted in the GARTEUR Action Group HC/AG-24 to address noise scattering of helicopter rotors in presence of the fuselage. The focus of the Action Group is on the development and validation of numerical prediction methods and establishing an experimental data base for numerical validations. The numerical methods applied by most partners solve the Helmholtz equation using a Boundary Element Method for addressing the discretized Green’s function integral formulation of the solution. The test activities are conducted in the DLR Acoustic Wind Tunnel in Braunschweig (AWB), including acoustic scattering tests by spheres and a generic helicopter model. In the current paper, the results from the numerical simulations, the wind tunnel tests as well as numerical and test comparisons are addressed. The test configurations include the spheres with sting support and a finite NACA0012 wing (thanks to share data with a NATO STO group). The acoustic predictions of the scattering by spheres will be compared with the analytic solution to address the influence of the sphere support systems at different wind speeds. The acoustic predictions of the scattering by NACA0012 wing will be analyzed and compared to available test results for different source locations and frequencies.