Lateral aerodynamic interference between an interior train and a flat box bridge-deck

Abstract

This paper studies the crosswind aerodynamics of an interior train and flat box bridge-deck system via a series of wind tunnel experiments in wind angle of attack α = [−12°, 12°]. Aerodynamics of the train- and bridge-only models is measured as benchmarks under similar conditions. Upon comparing with the train- and bridge-only cases, the lateral aerodynamic interference between the train and bridge-deck is qualitatively identified by smoke-wire visualization and quantitatively detected by surface pressure and flow profiles located 8 mm upstream from the train model and 490 mm downstream from the bridge-deck model. Generally, the lateral aerodynamic interference on the train model is primarily manifested by suppression of underbody vortex shedding, shielding effect of bridge-deck leading-edge, and quasi-Reynolds number effect. Compared to the train-only case, the suppression of underbody vortex shedding reduces fluctuating drag, lift, and moment coefficients, whereas the shielding effect decreases the mean drag coefficient. The quasi-Reynolds number effect, owing to the accelerated and turbulent approaching flow over the rounded shoulder of the train model as α varies, abruptly alters drag, lift, and moment coefficients mimicking the classical Reynolds number effect, while the inflow Reynolds number remains unchanged. On the other hand, the lateral aerodynamic interference on the bridge-deck model is chiefly presented as flow transition promoting effect and intensifying effect on bridge-deck trailing-edge flow separating. Compared to the bridge-only case, the flow transition promoting effect leads to the global centerline of the bridge-deck aerodynamics to be parallel shifted about 4° to the positive direction of α, while the intensifying effect increases fluctuating drag, lift, and moment coefficients. Finally, the aerodynamics of the whole train-bridge system is briefly discussed.