Numerical Study of the Hydrodynamics of Waves and Currents and Their Effects in Pier Scouring

Abstract

The scour around cylindrical piles due to codirectional and opposite waves and currents is studied with Reynolds Averaged Navier–Stokes (RANS) equations via REEF3D numeric modeling. First, a calibration process was made through a comparison with the experimental data available in the literature. Subsequently, not only the hydrodynamics, but also the expected scour for a set of scenarios, which were defined by the relative velocity of the current ( U C W ), were studied numerically. The results obtained show that the hydrodynamics around the pile for codirectional or opposite waves and currents not have significant differences when analyzed in terms of their velocities, vorticities and mean shear stresses, since the currents proved to be more relevant compared to the net flow. The equilibrium scour, estimated by the extrapolation of the numerical data with the equation by Sheppard, enabled us to estimate values close to those described in the literature. From this extrapolation, it was verified that the dimensionless scour would be less when the waves and currents are from opposite directions. The U C W parameter is an indicator used to adequately measure the interactions between the currents and waves under conditions of codirectional flow. Nevertheless, it is recommended to modify this parameter for currents and waves in opposite directions, and an equation is proposed for this case.

The Equilibrium Scour Depth around a Pier under the Action of Collinear Waves and Current

“…Here, the equilibrium scour depth is obtained by equating the work done by the flowing fluid while interacting with the pier under the action of the collinear waves and current and the work done by the total volume of the sediment particles removed from the scour hole, respectively. Finally, the non-dimensional scour depth values estimated using the proposed analytical model are verified with the experimental and numerical results reported by Sumer and Fredsøe [30] and Quezada et al [39], respectively.…”

“…The proposed analytical model for the equilibrium scour depth is validated with the experimental data provided by Sumer and Fredsøe [30]and the numerical results reported by Quezada et al [39], respectively. Since the present model is developed for the collinear waves and current, it can be safely assumed that the flow hydrodynamics around the pier varies only along the x and z directions and the variations along the y direction are not taken into consideration.…”

“…The non-dimensional scour depths under co-directional waves and current as obtained from the numerical investigations by Quezada et al [39] are further utilized for the validation of the proposed model. Table 2 presents the comparison between the non-dimensional scour depths as found from the proposed analytical model and the numerical model illustrated by Quezada et al [39].…”

“…The non-dimensional scour depths under co-directional waves and current as obtained from the numerical investigations by Quezada et al [39] are further utilized for the validation of the proposed model. Table 2 presents the comparison between the non-dimensional scour depths as found from the proposed analytical model and the numerical model illustrated by Quezada et al [39]. To exactly represent the situation adopted by Quezada et al [39], the calculations are performed considering a vertical pier of diameter 0.2 m placed in a channel of width 1 m and carrying the flow at a depth of 0.5 m, respectively.…”

“…Table 2 presents the comparison between the non-dimensional scour depths as found from the proposed analytical model and the numerical model illustrated by Quezada et al [39]. To exactly represent the situation adopted by Quezada et al [39], the calculations are performed considering a vertical pier of diameter 0.2 m placed in a channel of width 1 m and carrying the flow at a depth of 0.5 m, respectively. The values of the unit weight of the water, unit weight of the bed material, bed-porosity and the mass density of the water mentioned earlier remains unchanged.…”