Aeroacoustics of a high-speed train double model at high Reynolds numbers

Abstract

The here presented wind tunnel study focuses on the Reynolds- and Mach number dependence on the aeroacoustic noise emitted by the first bogie of the 1 : 25 scaled model of the Next Generation Train. The knowledge of the aeroacoustic scaling is essential for the correct interpretation of measurements with down-scaled models. For the sound source analysis the microphone array technique is applied. To achieve comparable aerodynamic conditions, the Reynolds number realised with the scaled model must be similar to the one obtained for the full-scale train. Therefore, cryogenic wind tunnel measurements were conducted for which the Reynolds number was increased by cooling the fluid. In addition, this facility admits to vary the Mach- and Reynolds numbers independently, which is very valuable to gain insight into the aeroacoustic scaling, without changing the scale of the model. A double-model setup is used, which provides a realistic underfloor flow. The analysis of the acoustic spectra reveal strong tonal components, which are sensitive to variations of the Mach - and Reynolds number.