Turbulent Flow Field around a Cylindrical Pier on a Gravel Bed

Turbulent flow around a circular pier on a gravel bed is investigated experimentally, using particle image velocimetry. The turbulent kinetic energy (TKE), Reynolds shear stress (RSS), and vorticity are examined to understand the effect of flow depth (h) to pier diameter (d) ratio and flow intensity. Additionally, spectrum analysis is carried out to examine the vortex intensity over various frequencies of eddies. Mixing of the horseshoe vortex and surface roller is observed in the upstream of pier for h/d<4.33. Consequently, two opposite rotating vortices reduced the turbulence strength. The critical limit of h/d on a gravel bed is found to be three times more than that of a sand bed. Both TKE and RSS increased approximately linearly with flow intensity. Further, vortex shedding frequency and energy of vortices increased with h/d which attributed to an increase in the normalized equilibrium scour depth. The present study will be resourceful for researchers in developing scour models for gravel bed by giving more insights into the flow hydrodynamics with respect to approach flow parameters.