Abstract: The parts of the high-speed train wheelset located outside the bogie cavity are exposed to the unsteady air flows. Due to this strong flow impact, the large aerodynamic noise is generated around the wheelset. The flow and flow-induced noise behaviour around the isolated wheelset and the tandem wheelsets are investigated at a scaled model. For the isolated wheelset case, results show that due to vortex shedding and flow separation, the coherently alternating shedding vortices are generated from the axle whereas the wheel wake is dominated by the irregular vortices with different scales. The volume dipole is the predominate source of the quadrpole noise generated in the wheelset wake. Moreover, it is found that good agreement is achieved between numerical simulation and experimental measurement. The dipole noise produced from the pressure fluctuations on the wheelset wall surfaces is the main aerodynamic noise source. Corresponding to the dominant frequencies of the oscillating lift and drag forces from the wheelset, the frequency of the first harmonic peak of the radiated tonal noise is twice the shedding frequency from the axle. The aerodynamic noise generated from the axle is much higher than that from the wheel, leading to a typical dipole pattern in the far-field noise directivity. The inclusion of wheelset rotation increases the radiated noise levels around 2 dB with similar directivity compared with the stationary wheelset. For the tandem-wheelset case, the flow-induced noise behaviour of the upstream wheelset is similar to the isolated wheelset case, whereas the rear wheelset is submerged in the upstream wheelset wake and situated in a turbulent condition, and thus the irregular flow feature makes the noise radiation more broadband and multi-directional with lower noise amplitude level.

Key words: aerodynamic noise prediction, flow behaviour, railway noise, simplified train wheelset