Toki Uda

Reduction of Aerodynamic Noise Emitted from Pantograph by Appropriate Aerodynamic Interference Around Pantograph Head Support

Reduction of aerodynamic noise emitted from a pantograph head and its support is one of the important subjects for the speed-up of high-speed trains from an environmental point of view. In this study, to reduce aerodynamic noise emitted from the pantograph head and its support, suitable arrangement of a pantograph head which has a smooth cross section profile, was investigated. The flow field measurement in the wake domain of the pantograph shows that turbulent intensity can be reduced by setting the pantograph head at a suitable position. The reduction of turbulence in the wake domain is caused by appropriate aerodynamic interference between the pantograph head and its support. Furthermore, the results of the aerodynamic noise measurement show that the suitable pantograph head arrangement efficiently reduces aerodynamic noise.

Estimation of Aerodynamic Bogie Noise Through Field and Wind Tunnel Tests

A method has been developed to determine the aerodynamic noise from the bogie of a high-speed train using a two-dimensional microphone array in a wind tunnel. First, the flow velocity under the train car in the rail direction was measured in a field test. Second, the flow distribution was simulated in the wind tunnel. Third, aerodynamic noise generated by a bogie was estimated from the source distribution measured using a two-dimensional microphone array. Finally, the noise generated from the lower part of the car, which was obtained by adding the aerodynamic noise and the rolling noise estimated by the TWINS model, was compared with the result obtained from the field test. It was found that the estimated noise shows good agreement with the measurement obtained in the field test. The estimated lower part noise levels were consistent with the actual experimental measurements. This conclusion suggests that this method is appropriate to estimate aerodynamic bogie noise quantitatively. It is also shown that below 500 Hz the contribution of the aerodynamic bogie noise is more than those of the rolling and machinery noise.

Improvement of the Source Localization Accuracy by Microphone Array Adjacent to Main Flow of Wind Tunnel

In this study, we proposed a method to improve an accuracy of source localization in a wind tunnel tests by using microphone array. Based on an acoustic path model in passing through the free shear layer, the microphone array is installed adjacent to the main flow to avoid the refraction and dissipation in the free shear layer. The flow-induced noise caused by the interference with the main flow is also effectively reduced by calculating a cross spectrum between the respective outputs of 2 pairs of 2-D microphone array. The effects of these techniques are varified by the acoustic performance test with standard source device under wind condition. As a result, firstly, it was found out that the calculation method is effective even at the uniform wind velocity of 300 km/h and enables the acoustic measurement adjacent to the main flow. Secondly, accurate noise source localization can be achieved by installing the microphone array along the line extended from the side wall of the wind tunnel nozzle adjacent to the main flow. The location error by this method is improved less than 10 mm compared with that measured outside of the free shear layer.