Engineering, Japan
Engineering, Japan

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Yamazaki N.,Noise Analysis Laboratory | Kitagawa T.,Noise Analysis Laboratory | Uda T.,Noise Analysis Laboratory | Nagakura K.,Environmental Engineering Division | And 2 more authors.
Quarterly Report of RTRI (Railway Technical Research Institute) | Year: 2016

A method has been developed for predicting the aerodynamic noise from the bogie of a high-speed train using a two-dimensional microphone array in a low-noise wind tunnel. First, the flow velocity in the rail direction was measured in a field test at several points along the sleeper direction under the train car. Second, the flow distribution was reproduced precisely in a low-noise wind tunnel. Third, aerodynamic noise generated by the bogie ("aerodynamic bogie noise") was estimated from the noise source distribution measured with a twodimensional microphone array. Finally, based on the experimental results, the noise generated from the lower part of the car (i.e. the aerodynamic noise estimated through the proposed method and the rolling and machinery noise estimated in a previous study) was compared with field test data measured near the track. The estimated lower part noise levels showed good agreement with those measured in the field test. This suggests that the proposed method is valid for the quantitative estimation of aerodynamic bogie noise. It was also shown that the contribution of the aerodynamic bogie noise is greater than the rolling and machinery noise, especially in the low-frequency region.

Mitsumoji T.,Current Collection Laboratory | Sato Y.,Current Collection Laboratory | Ikeda M.,Railway Dynamics Division | Sueki T.,Noise Analysis Laboratory | Fukagata K.,Keio University
Quarterly Report of RTRI (Railway Technical Research Institute) | Year: 2014

Reducing aerodynamic noise emitted from a pantograph head is an important environmental factor to be examined in the light of increasing the running speed of Shinkansen trains. This paper discusses control of flow around the pantograph head using plasma actuators. The results of the wind tunnel tests show that plasma actuators can prevent flow separation from the pantograph head surface and weaken Karman vortices. In addition, CFD results indicate that the plasma actuators can reduce aerodynamic noise emitted from the pantograph head.

Takaishi T.,Noise Analysis Laboratory | Ikeda M.,Current Collection Laboratory
Quarterly Report of RTRI (Railway Technical Research Institute) | Year: 2012

Differences in flow conditions between wind tunnel tests and actual trains sometimes generate significant errors in the estimation of aerodynamic noise from devices such as pantographs and also of aerodynamic forces acting on them. In this study, turbulent flow conditions around a current collector of an actual running train were measured first. An experimental method was then developed which places obstacles upstream from the test section in a wind tunnel in order to simulate turbulent flows. Finally, the aerodynamic noise and forces acting on a pantograph model were evaluated with and without the obstacles, which confirmed that the proposed method for wind tunnel tests simulated conditions of the actual train well.

Ikeda M.,Current Collection Laboratory | Mitsumoji T.,Current Collection Laboratory | Sueki T.,Noise Analysis Laboratory | Takaishi T.,Noise Analysis Laboratory
Quarterly Report of RTRI (Railway Technical Research Institute) (Japan) | Year: 2010

To reduce the aerodynamic noise generated by a pantograph, which is one of the dominant noise sources in high speed trains, the authors have proposed a set of noise reduction techniques, namely, shape-optimization of the panhead, relaxation of aerodynamic interference between the panhead and the articulated frame, and the use of porous material for surface covering. To evaluate the total noise reduction effect of these techniques, they were applied to a prototype pantograph which was tested in a wind tunnel. Test results showed that the prototype pantograph lowered the noise level from the current low-noise pantograph by about 4dB. Furthermore, they also confirmed that the prototype pantograph had sufficient aerodynamic stability against change of attack angle.

Ogata Y.,Noise Analysis Laboratory | Nagakura K.,Noise Analysis Laboratory
Quarterly Report of RTRI (Railway Technical Research Institute) | Year: 2012

Recently, complaints regarding railway noise have increased from residents living in high-rise buildings facing railway tracks. However, reducing noise for locations high above the tracks with conventional noise barriers is difficult, because the noise sources are directly visible from these elevated positions. This paper investigated the effect on noise of low barriers installed adjacent to rails. It was evident through acoustic tests using scale models and field tests on existing railways that this type of noise barrier is able to reduce noise even in locations high above the track. Furthermore, a prediction model of the effect of these noise barriers was proposed based on the results of the field tests.

Kitagawa T.,Noise Analysis Laboratory | Thompson D.J.,University of Southampton
Quarterly Report of RTRI (Railway Technical Research Institute) (Japan) | Year: 2011

Theoretical models, such as TWINS developed in Europe, and microphone array measurements have been widely used to gain better understanding of rolling noise. However, the array measurements are often inconsistent with the TWINS predictions and give less prominence to the rail than the TWINS models. The objectives of this paper are to find out whether the microphone array measurements give a correct estimate of sound power radiated by the rail. Through the analysis of the performance of a microphone array, it has been found that a horizontal array focused normal to the rail cannot detect a large part of the noise from the rail in high frequency range where free wave propagation occurs in the rail. It is concluded that the results obtained by using microphone arrays do not reflect the radiation characteristics of the noise from a rail, and this leads to the underestimation of the contribution of the rail component of noise.

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