Fast-moving water can erode sand, soil, and sediment around bridge abutments and piers, resulting in holes. This scour is one of the most common reasons for bridge failure. In coastal environments, surface waves can impact particle movement, shear stress, and momentum transfer, among other flow properties. In a literature review, the authors of a recent journal paper in the Journal of Waterway, Port, Coastal and Ocean Engineering determined that previous studies primarily focused on examining the impact of wave superposition on the turbulent flow field over a static bed. Little research has explored turbulent conditions in a moving sediment bed.
Researchers Gaurav Misuriya, T. I. Eldho, and B. S. Mazumder look at how the Keulegan–Carpenter number (which helps calculate wave forces on offshore platforms) relates to the turbulent characteristics of a mobile bed. Their lab experiment included a rectangular channel with a centrifugal pump to maintain a steady discharge and a transparent sediment bed. In their paper, “Turbulent Flow Field and Scour Characteristics around Bridge Pier in Combined Wave and Current Conditions,” the researchers tested three different wave conditions and employed a laser and cameras to measure the particle image velocimetry. Learn more about how this research can help engineers account for combined wave and current flow conditions when designing piers in coastal areas. Get the full the results of their research at https://doi.org/10.1061/JWPED5.WWENG-2101. The abstract is below.
Abstract
This experimental study investigates the effect of surface waves that are superimposed on a unidirectional current around a bridge pier in a gravel bed, which employs particle image velocimetry (PIV). A comprehensive examination of various flow characteristics, which include the intermittency factor (IF), turbulent kinetic energy (TKE), and vorticity analysis, is conducted to elucidate the variations around the pier with respect to the Keulegan–Carpenter (KC) number. The findings reveal a correlation between the KC number and the flow dynamics in combined conditions: specifically, due to combined wave–flow conditions, escalation in the frequency of vortices near the pier and the increment in turbulent strength, in terms of the TKE. Of note, this augmentation in turbulent strength is associated with an increase in the KC number. At a low KC number, the maximum scour depth occurred downstream near the pier, which shifted to upstream with an increase in the KC number. In addition, the results could be utilized for the development and validation of numerical models, which accurately estimate the local scour under combined flow conditions.
Get the complete research on how to account for combined wave and current flow conditions when designing piers in coastal areas in the ASCE Library: https://doi.org/10.1061/JWPED5.WWENG-2101.
