Aerodynamic characteristics of two noise barriers (fully enclosed and semi-enclosed) caused by a passing train: A comparative study

Abstract

With the wide use of noise barriers along high-speed railways, the aerodynamic problems of noise barrier caused by high-speed train operation become increasingly prominent. At present, the commonly used noise barrier types of high-speed railway can be classified as fully enclosed and semi-closed (inverted ‘L’ type). The model test of high-speed moving train with scale ratio of 1:16.8 was conducted, and the temporal and spatial laws of aerodynamic pressure of fully enclosed and semi-enclosed noise barriers were compared. These processes were performed to study the difference in the aerodynamic pressure characteristics of noise barriers when high-speed trains at speeds of 350 km/h pass through the two types of noise barriers. On the basis of large eddy simulation turbulence model and ‘mosaic’ grid technology, the corresponding 3D computational fluid dynamics numerical model of train–noise barrier–bridge was established, and the corresponding improvement schemes were proposed to solve the phenomenon of unreasonable pulsation pressure distribution of fully enclosed and semi-enclosed noise barriers. The pressure relief mechanism of the pressure relief hole on the fully enclosed noise barrier and the buffer mechanism of the buffer structure at the end of the semi-enclosed noise barrier are revealed from the perspective of flow field. The main results show that: (1) Compression wave and expansion wave are the key factors affecting the change in the peak pressure inside the fully enclosed noise barrier, while the pressure of the semi-enclosed noise barrier is directly affected by slipstream of the train. (2) The pressure amplitude in the middle of the fully enclosed noise barrier is 2.1–2.7 times of that at the two ends. The amplitude of transverse force at the two ends of semi-enclosed noise barrier is 1.2–1.4 times of that in the middle. (3) In the longitudinal direction of the noise barrier near the train side, the pressure of the measuring point of the semi-enclosed noise barrier decreases with the increase in the measuring point height; The pressure in the middle section of the fully enclosed noise barrier is unaffected by the height of the measuring point. (4) A triangular buffer structure can effectively alleviate the unreasonable vertical pressure distribution phenomenon caused by the train bursting into the semi-closed noise barrier, and the reduction rate of the transverse force amplitude of the end noise barrier is as high as 21.44%. (5) The pressure relief scheme of three holes can effectively alleviate the phenomenon of excessive pressure amplitude in the middle of the fully enclosed noise barrier caused by the passing train, and the reduction rate of pressure amplitude can reach up to 60.5%. The pressure relief holes with an area of 1.7 H × 1.7 H are arranged at 0.25, 0.5, and 0.75 L, where L is the longitudinal length of the noise barrier.