Numerical Study On The Characteristics Of Compression Waves Produced By High-speed Trains In Tunnel Based On One-dimensional Flow Model

Initial Compression waves are generated at the nose of high-speed train when it enters atunnel. As the initial compression waves propagate to the tunnel exit at a local speed of sound,they will be reflected and refracted at tunnel exit. The refracted compression waves whichradiate into the surroundings are called micro-pressure waves (MPWs).The MPWs willbecome sonic booms if they are strong enough, they will seriously affect the nearby occupantsand environment. The strength of MPWs is proportional to the rate of change of pressure ofcompression waves which reaches the tunnel exit. At present, a very importantcountermeasure to alleviate the MPWs is to alleviate the initial compression wave, so it isnecessary to know the formation, propagation process in tunnel and the influencing factors ofinitial compression wave.With the one-dimensional compressible unsteady non-homentropic flow model, theeffective cross-sectional area of air flow in tunnel is considered as the function of the flowingtime and flowing distance in this paper. The divisiory and processing methods of mesh systemare improved, and the aerodynamic problem when a streamline high-speed train enters thetunnel portal can be simulated actually. According to the propagation characteristics of initialcompression wave in tunnel, the improved method of characteristics of generalized Riemannvariable is applied to calculate the initial compression wave, it can reduced the numericaldissipation effectively.The high-speed train ICE2is taken as an example to refit the area function of train head,the correctness of this fitting method is verified by comparing with the experimental data. Thedifferences between CRH3and CRH380A are analyzed and their area function of train headsare given with the same method of ICE2, so we obtain the aerodynamic train heads which aresuitable for calculating the pressure wave with one-dimensional model. The generationcharacteristics of initial compression waves when CRH3and CRH380A enter the tunnel arestudied in this paper, and also the influence of train head, train speed and blockage ratio onthe wavelength and propagation of initial compression wave are analyzed. Combine thecharacteristic of the rate of pressure change when the initial compression wave propagates intunnel, the critical tunnel length is obtained with different speed and models of train.The programs to calculate the generation and propagation of initial compression waveare improved in this paper. Also, the fit method of area function is improved, the generationand propagation characteristics of initial compression wave are further analyzed. Someresearch methods and conclusions of this paper can provide a beneficial reference for thefurther research and application.