Parameter study and optimization design of a hat oblique tunnel portal

Abstract

The present work focuses on the aerodynamic problems resulting from a high-speed train (HST) passing through a tunnel. Numerical simulations were employed to obtain the numerical results, and they were verified by a moving-model test. Two responses, ${\Delta C}_p$ (coefficient of the peak-to-peak pressure of a single fluctuation) and ${ P}_{\mathit{mpw}}$ (pressure value of micro-pressure wave), were studied with regard to the three building parameters of the portal-hat buffer structure of the tunnel entrance and exit. The MOPSO (multi-objective particle swarm optimization) method was employed to solve the optimization problem in order to find the minimum ${\Delta C}_p$ and ${ P}_{\mathit{mpw}}$ . Results showed that the effects of the three design parameters on ${\Delta C}_p$ were not monotonous, and the influences of $\alpha$ (the oblique angle of the portal) and $h$ (the height of the hat structure) were more significant than that of $\mathrm{ }\beta$ (the angle between the vertical line of the portal and the hat). Monotonically decreasing responses were found in ${ P}_{\mathit{mpw}}$ for $\alpha$ and $\mathrm{ }\beta$ . The Pareto front of ${\Delta C}_p$ and ${ P}_{\mathit{mpw}}$ was obtained. The ideal single-objective optimums for each response located at the ends of the Pareto front had values of 1.0560 for ${\Delta C}_p$ and 101.8 Pa for ${ P}_{\mathit{mpw}}$ .