Investigation of the velocity and pressure fluctuations distributions inside the turbulent horseshoe vortex system around a circular bridge pier

摘要

Large eddy simulation with a dynamic sub-grid scale model is used to study the spatio-temporal structure of the horseshoe vortex (HV) system around a bridge pier of circular section in a shallow channel with a flat bed. It is found that the structure of the turbulent HV system varies considerably in space and time, though, typically, a relatively stable, necklace like vortical structure (primary vortex) is present around the upstream face of the cylinder and oscillates randomly. The simulation captures the presence of bimodal aperiodic chaotic oscillations inside the HV system region, as well as the sharp increase in the resolved velocity fluctuations and pressure fluctuations observed in previous experimental investigations of high Reynolds number junction flows. It is observed that in the bimodal region the histogram of the velocity fluctuations displays a double-peak shape for all the velocity components except the one along the core of the primary HV.