Large eddy simulation of Reynolds number impact on streamlined high-speed train flows

This study utilizes large eddy simulation (LES) to examine the impact of Reynolds number on the aerodynamic performance of a streamlined simplified Intercity-Express 3 (ICE3) high-speed train. Simulations are conducted for Reynolds numbers within 0.3 x 10(5 )<= Re-H <= 1.8 x 10(5). Validation against wind tunnel experiments shows consistent trends in the mean base pressure coefficient, with maximum errors below 3.6%, confirming the accuracy of the LES method. Results reveal that, while flow separation at the tail generates similar vortex patterns across the Reynolds numbers studied, quantitative assessments reveal a pronounced influence of the Reynolds number on wake velocity distributions and surface pressure profiles. As Reynolds number increases, the drag and lift coefficients decline, along with reduced fluctuations of force coefficients and non-dimensional turbulent kinetic energy in the wake. Additionally, significant changes in near-wall wake structures and flow attachment patterns are observed. The results highlight the importance of considering Reynolds number variations in the design and optimization of high-speed trains.