an investigation of influence of windshield configuration and train length on high-speed train aerodynamic performance

The aerodynamic performance of four train models with different windshield configurations (i.e., internal and/or external) in three train marshalling modes (i.e., 3, 6 and 8-car groups) was numerically investigated in this study. the train's airflow characteristics at re=2.25×10^6 were determined using the shear stress transport (sst) k-𝜔 turbulence model. the results were validated by comparing the pressure distributions and drag forces on the streamlined heads with experimental data. the difference in windshield configuration and train length has a substantial influence on the train’s flow field and surface pressure distribution. for the trains with internal windshields, due to non-uniform geometry, the flow is separated and vortices are formed at the windshield area. the boundary layer profile increases with the increased train length, and its thickness varies with windshield configurations. asymmetric vortices are formed in the wake at a distance close to the tail car’s nose, except for trains with external windshields. the reduction of the flow velocity as the train length increases causes a reduction of the low pressure near the tail car’s streamline transition, thus causing a decrease in the tail car’s drag and lift forces. consequently, for trains with external windshields, the head car’s drag increases, whereas the total train drag reduces significantly as the train length increases. therefore, employing external windshields in all the inter-carriage gap sections, irrespective of the train length, demonstrates a good ability to reduce future train’s aerodynamic drag.