Field measurements and CFD simulations of wind characteristics at the Yellow River bridge site in a converging-channel terrain.

This paper is aimed at investigating the airflow over unusual converging-channel terrain that includes a deep valley on the up-river side and a flat plain on the down-river side. A computational fluid dynamics (CFD) simulation with standard k–ε model was applied to study the variation of wind structure from the important approach wind directions. A long-period of field measurements provided supplementary data from a Sodar system and also 2D ultrasonic anemometers. Broad agreement was found between the observations and the CFD simulations. The results show that a wind speed-up was generated in the valley and its exit, whose magnitude was sensitive to the approaching wind direction, and that terrain-induced effects on wind direction are significant within the height range up to 200 m. It is also found that the wind speeds and directions along the entire bridge structure, including the spanwise deck and the bridge towers, is non-homogeneous due to the effects of the complex terrain. Moreover, through comparing the predicted wind speed at this bridge site, it was found that the Chinese national code recommends a lower speed than CFD simulations for the two worst approach directions which are normal to the bridge axis. [ABSTRACT FROM AUTHOR]