Shielding and internode effects of truss bridge on the aerodynamic characteristics of high-speed train under crosswinds

Accurately simulating the aerodynamic characteristics is important to the safety and stability of high-speed train, especially when it operates under strong crosswinds. In recent, long span highway-railway bridge has been developed rapidly to enable the high-speed rail to cross wide rivers and valleys, where the truss bridges are usually served as the main girder type. This study aims to investigate the unique interference effects on the aerodynamic characteristics of the high-speed train caused by the truss bridge, i.e., the so-called shielding effect and internode effect. The shielding effect of the truss bridge on the mean aerodynamic coefficients is firstly quantified based on a moving train model test in wind tunnel. Combined with a 3-D computational fluid dynamic (CFD) model validated by the wind tunnel test, a series of numerical simulations are conducted to study the mechanism of internode effect, where the airflow field and pressure distributions around the train body and on the bridge surface are interpreted. The results reveal that the truss bridge has an obvious whole and local shielding effects, with the first effect introducing a remarkable decrease on the aerodynamic forces of trains at the entrance and the second effect leading to an intermittent excitation.