Turbulence statistics of flow causing scour around circular and oblong piers

In this study, experimental investigations of the flow pattern around an oblong pier (OP) mounted on a rigid flat surface are carried out in a laboratory flume and the results are compared with that of a circular pier (CP) for better understanding of the flow hydrodynamics applicable to scour. The novelty of this work is the study of turbulence characteristics such as mean velocities, Reynolds stresses, turbulent kinetic energy and the contributions of burst-sweep cycles to the total Reynolds shear stresses along the oblong and the circular piers and their inter-comparison, which have not been previously addressed. Application of power spectral analysis suggests that the peak values of vortex shedding frequency for OP are higher than those of CP, indicating lower wake instabilities for OP. The influence of perturbed flow around the CP is considerably higher than that of OP, resulting in more scour around the CP, under identical flow conditions.