Aerodynamic Performance of Different Metro Train Geometries through a Straight Tunnel Based on Steady and Unsteady Reynolds-Averaged Navier-Stokes Modeling

Numerical RANS modeling has been carried out to assess the aerodynamics of different metro train geometries through a straight tunnel. A steady-state approach was first used to choose the best geometry out of seven alternatives in terms of drag reduction when compared with a typical blunt face train design representative of European metro networks. The proposed models have different edge-rounding characteristics at the front and rear faces. Afterward, the baseline and optimized geometries are compared at different train velocities, and the flow structure surrounding the models is discussed using unsteady RANS results. The study focuses on skin and pressure drag coefficients for trains traveling at 40 km h⁻¹ in a straight tunnel with a blockage ratio of 0.69. All the considered alternatives show a drag reduction between 5% and 20% relative to the baseline case.