INVESTIGATION OF HYDRODYNAMICS AND SCOUR AROUND BRIDGE PIERS UNDER THE COMBINED WAVE AND CURRENT EFFECTS

Abstract

Bridges piers and other marine structures in coastal regions are affected by water currents and waves. These structures may collapse due to scour induced by water currents or waves, leading to huge economic and life losses. The problem worsens when surface waves are superimposed on current. The superposition of the wave further modifies the flow field around the bridge pier. A thorough understanding of turbulent flow under these circumstances will be crucial for the cost-effective and ideal design of the pier. This study experimentally investigates the effect of the superposition of surface wave on the flow hydrodynamics and the local scour around a circular pier over a gravel bed. It also presents the comparison of turbulence characteristics under only current condition and combination of wave and current. Laboratory experiments were performed in a 15 m long rectangular flume. A surface wave with frequency of 0.5 Hz was superimposed in the direction of current. The instantaneous velocity data for evaluating turbulent kinetic energy was recorded using particle image velocimetry (PIV). The analysis of the result showed that the superposition of surface wave significantly increased the turbulence strength which leads to approximately 30% increase in the local scour depth. This study will be helpful in optimal design of bridge piers and other coastal structures by improving the relationship for the scour prediction in coastal area and provide a data set for the numerical simulation of the problem as well.