Study of Shock Tube for Wave Phenomenon in High Speed Railway Tunnel(II)-attenuation and Nonlinear Effect of Compression Waves-

고속철도 터널에서 발생하는 파동현상에 관한 충격파관의 연구(2)-압축파의 감쇠와 비선형효과-

As a railway train enters a tunnel at high speed, a compression wave is formed in front of the train and propagates along the tunnel. The compression wave subsequently emerges from the exit of the tunnel, which causes an impulsive noise. The impulsive noise is closely related to the pressure gradient of the compression wave propagating the tunnel. In order to investigate the characteristics of the compression waves, in the present study an experiment was made using a shock tube. The results show that the strength of a compression wave decreases with the distance from the tunnel entrance and the nonlinear effect of compression wave appears to be significant if strength of the initial compression wave is greater than 7 kPa. Furthermore if the wave pattern is known, attenuation of the compression wave propagating in a tunnel can be reasonably predicted by a theoretical equation considering viscous action and heat transfer in boundary layer.