This study investigates the allevia

This study investigates the alleviation effect of partially enlarged cross-section on tunnel aerodynamics. By comparing the numerical results to moving model tests data, the SST k-ω turbulence model and hybrid grid are used for the numerical simulations of high-speed train passing through tunnel. The reduction effects of three parameters for the enlarged section are analyzed, i.e., length, cross-sectional area, and slope. Systematic numerical simulations show that the terminal location of the enlarged section should be close to the location of the initial compression wave amplitude along tunnel length direction. The reduction rates of the pressure transient amplitude and the average pressure variation follow a second order polynomial equation with the increase of the enlarged section area, and increase with the increase of enlarged section slope. Positive enlarged section slope is applied for reducing pressure transients in the tunnel. Furthermore, an engineering application equation is proposed, with which the reduction rates of enlarged sections on the pressure transient amplitude and the average pressure variation can be estimated effectively. The equation generalized in this study could well guide the tunnel design process.