Improving the performance of aeroacoustic measurements beneath a turbulent boundary layer in a wake flow

Experimental measurement and subsequent numerical prediction of the excitation of at plates or car windows beneath a turbulent boundary layer have become important for the development of novel cars and airplanes. A wavenumber spectrum can be used to define the load on a plat caused by the pressure fluctuations on the surface. Wavenumber spectra from measurements are used to validate the numerical predictions of the acoustic and hydrodynamic portions of the pressure fluctuations. When measuring wavenumber spectra, the design of the experiment can have a large in fluence on the outcome. In this paper, the effects of both array design and the application of deconvolution algorithms on the experimental determination of the wavenumber-frequency spectrum are evaluated

Prediction of contra-rotating open rotor broadband noise in isolated and installed configurations

Broadband noise is a significant part of the noise emitted by contra-rotating open rotors. Several noise sources can contribute to the total broadband sound field, with the most dominant ones probably being trailing edge noise, rotor-wake interaction noise and pylon-wake interaction noise. This paper addresses the prediction of these noise sources using analytical models based on Amiet’s flat plate airfoil theory and also to empirical turbulence models, fed by input data extracted from steady and unsteady CFD RANS simulations. The models are assessed against wind tunnel tests of Rolls-Royce’s rig 145 (build 1) conducted at the DNW anechoic open jet test facility using Rolls-Royce blades and Airbus pylons. The study showed promising results in terms of the ability of the models to predict acoustic power spectrum shapes, peak frequencies and absolute levels. The effects of changes in thrust on broadband wake-interaction noise are well reproduced. However, the models significantly underestimate the effect of thrust on trailing edge noise and the effect of rotational velocity on pylon interaction noise