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Engineering, Japan

Miyachi T.,Vehicle Aerodynamics Laboratory
Quarterly Report of RTRI (Railway Technical Research Institute) (Japan) | Year: 2011

This paper introduces a simple prediction model for a micro-pressure wave emitted from a tunnel portal. A theoretical analysis was made of the micro-pressure wave produced when a high-speed train goes through a tunnel, considering the effects of topography around the tunnel portal. Sources of the micro-pressure wave are expressed in the terms of a monopole and a dipole. Model predictions were consistent with the model experiments where the exact Green's function was determined by the method of image. Source

Suzuki M.,Vehicle Aerodynamics Laboratory | Hibino Y.,Vehicle Dynamics Laboratory
Quarterly Report of RTRI (Railway Technical Research Institute) | Year: 2016

Natural winds are turbulent flows and boundary layers exist near the surface of the actual ground, so that there is a possibility that the aerodynamic forces acting on train/vehicles from natural winds differ from uniform flows. Accordingly, full-scale models of a train/ vehicle and a viaduct were constructed in a windy area, and wind characteristics and aerodynamic forces acting on the vehicle models were measured. Wind tunnel tests were conducted to simulate the turbulent boundary layer flow, and these test results agreed well with field tests. Source

Yamazaki N.,Noise Analysis Laboratory | Kitagawa T.,Noise Analysis Laboratory | Uda T.,Noise Analysis Laboratory | Iwasaki M.,Vehicle Aerodynamics Laboratory
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. Source

Nakade K.,Vehicle Aerodynamics Laboratory
Quarterly Report of RTRI (Railway Technical Research Institute) | Year: 2014

In order to investigate the running effects on aerodynamic characteristics of a railway vehicle under strong cross winds, the author performed Large-Eddy Simulation of flow around a simple running train model. To simulate the cross winds which affect a running train, the author used an inflow turbulence generation technique based on an unsteady flow simulation method in the frame of a train moving coordinate system. In the case where the train speeds are 10m/s, 5.8m/s, 1.8m/s and 0m/s and the wind speed is 10m/s in the direction perpendicular to the train running direction, the pressure coefficient distribution on the surface of the running train was obtained by numerical simulation and compared with that from experimental studies. The detailed flow fields around the running train were also presented. Based on the comparison between the running train simulation and stationary train simulation with the same relative wind angles to the train, the running effects on aerodynamic characteristics in the case of the simple train model were discussed. Source

Sakuma Y.,Vehicle Aerodynamics Laboratory | Fukuda T.,Heat and Air Flow Analysis Laboratory | Ido Dr. A.,Vehicle Aerodynamics Laboratory
Quarterly Report of RTRI (Railway Technical Research Institute) | Year: 2013

Field measurements, wind tunnel experiments, and scale model launching experiments were conducted to improve the aerodynamic performance of flat-fronted trains on metergauge railway lines. The study centered mainly on the compression pressure waves generated by trains entering single-track tunnels and aerodynamic drag acting on the vehicle. Countermeasures to reduce the amplitude of the compression waves and their gradients and the aerodynamic drag were examined. Scale model launching experiments demonstrated that tunnel entrance hoods more than 8 m long - actual size - (about one and a half times the tunnel diameter) were an effective infrastructure measure for reducing the maximum compression wave pressure gradient (dp/dt)max by approximately 70% compared to tunnels with no hood. Running tests with real trains further demonstrated that attaching aerodynamic fins to the front end of a two-car test train traveling at 120 km/h was an effective onboard measure for reducing the separated flow region, (dp/dt)max by approximately 40%, and running resistance in the open environment by approximately. Source

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