Turbulent flow characteristics responsible for current-induced scour around a complex pier

Abstract

This study investigates the turbulent flow characteristics around a complex pier (CP) with an elliptical pile-cap to understand the mechanics of the flow responsible for current-induced scour. The velocity data are recorded using an acoustic Doppler velocimeter for a Reynolds number of 67 745. This study gives mean velocities in different horizontal and vertical planes, Reynolds stresses, turbulent kinetic energy, and spectral analysis around the CP. The streamwise spectra with vortex-shedding frequencies and corresponding Strouhal numbers are discussed for three distinct regions generated by CP. The elliptical pile-cap shields the downward flow at the upstream of the column and the upward-moving wakes at the downstream of the CP, responsible for the sediment entrainment around a pier. In comparison, the effect of perturbed flow around the CP was considerably less than that of the simple pier, resulting in less scour around the CP for identical flow situations.