Numerical investigation on an array of Helmholtz resonators for the reduction of micro-pressure waves in modern and future high-speed rail tunnel systems

Abstract

Previous research has proposed that an array of Helmholtz resonators may be an effective method for suppressing the propagation of pressure and sound waves, generated by a high-speed train entering and moving in a tunnel. The array can be used to counteract environmental noise from tunnel portals and also the emergence of a shock wave in the tunnel. The implementation of an array of Helmholtz resonators in current and future high-speed train-tunnel systems is studied. Wave propagation in the tunnel is modelled using a quasi-one-dimensional formulation, accounting for non-linear effects, wall friction and the diffusivity of sound. A multi-objective genetic algorithm is then used to optimise the design of the array, subject to the geometric constraints of a demonstrative tunnel system and the incident wavefront in order to attenuate the propagation of pressure waves. It is shown that an array of Helmholtz resonators can be an effective countermeasure for various tunnel lengths. In addition, the array can be designed to function effectively over a wide operating envelope, ensuring it will still function effectively as train speeds increase into the future

Influence of air chambers on wavefront steepening in railway tunnels

“…Indeed, the ability of the chambers to reduce large steepnesses rapidly (Fig- 5) opens up the possibility of installing them only in the regions of tunnel adjacent to exit portals as assumed by Tebbutt et al [17]. In principle, wavefronts generated further upstream would be allowed to shorten indefinitely until reaching the region with chambers, in which they would rapidly elongate.…”

“…It would be desirable to have an effective in-tunnel counter-measure, thereby avoiding visual and practical inconvenience outside portals. One such possibility was introduced by Sugimoto [16] and, in a different form, by Tebbutt et al [17]. These methods make use of Helmholtz resonators that hamper the transmission of higher frequencies in wavefronts.…”

Field test for micro-pressure wave reduction measurement by area optimization of windows of tunnel hoods

“…10 Alternative or additional countermeasures for mitigating MPWs by reducing the pressure gradient of the compression wave at the propagation stage include partially installing a ballast, 15 applying a branch shaft, 9,16 and installing Helmholtz resonators along the tunnel wall. 17,18 In Japanese convention, as shown in Figure 1, the tunnel hood configuration is such that the ratio between the crosssectional area of the hood and the tunnel is 1.4-1.6, the length of the tunnel hood is in the range 10 m-50 m, and its cross-sectional area is constant in the longitudinal direction.…”

Development of tunnel compression wave generator with multiple small solenoid valves

“…The steepening depends on the nonlinear effect of the fluid, boundary layer, tunnel configuration, etc. To attenuate the steepening, the influence of ballast, branches, resonators, and absorbers are studied (Ozawa et al (1997), Vardy and Brown (2000), , Tebbutt et al (2017)). In stage (c), the influences of the exit hood and topography of the ground near the exit portal have been studied , Miyachi (2016)).…”