パイプ内を伝播する圧力波から入射波と反射波を分離する方法に関する研究(流体工学,流体機械)  [in Japanese] Study on a Method of Separating Incident Wave and Reflected Wave from Combined Pressure Wave in a Pipe(Fluids Engineering)  [in Japanese]

While a train is running in a tunnel, a pressure wave (we call it "tunnel outside continuous wave") is radiated from both end portals to the outside space. Though some characteristics of the tunnel outside continuous wave are revealed from previous researches, the relation between the tunnel outside continuous wave and the pressure wave in a tunnel has not been obtained yet. A pressure wave measured at a fixed point in a tunnel is the superposition of two waves (the incidence wave and the reflected wave) propagating in opposite directions. Therefore, in order to investigate the relation between the tunnel outside continuous wave and the pressure wave in a tunnel, it is necessary to separate the incident wave or the reflected wave from the measured pressure wave. In this paper, we propose a method of extracting the incident wave or the reflected wave from the pressure waves in a tunnel propagating in both directions in a tunnel. The validity of this method has been confirmed by numerical and experimental investigation.