Numerical Simulation of Wave-Current Forces Acting on Cofferdam for Sea-Crossing Bridge Based on Large Eddy Simulation

The foundation construction of a sea-crossing bridge may encounter complex sea conditions, such as deep-water, large-wave and rapid-flow conditions. Wave-current forces may even become dominant loads for the cofferdam construction of a sea-crossing bridge. To study wave-current forces acting on cofferdams of sea-crossing bridges, a numerical model for simulation of three-dimensional (3D) wave-current interactions with a structure was established using the large eddy simulation method. In this model, the vertical multiple-layer σ-coordinate transformation model was used to track the 3D wave current-induced free surface, and the immersed boundary method (IBM) was added to deal with the irregular structural surface. The proposed 3D numerical model was then validated and applied to simulate oblique wave-current interaction with a rectangular bridge cofferdam under different length-width ratios. The results indicated that the established 3D numerical model could well simulate wave-current forces acting on the rectangular structure. When the length-width ratio equals 1.0, the incident angle has little effect on the total wave-current forces due to structural symmetry, with a growth below 5%. As the length-width ratio increases, however, the incident angle will have greater impact on the total wave-current forces acting on the rectangular cofferdam. At a length-width ratio of 2.0, the total force acting on the structure when wave current is incident along longitudinal direction (90°) are 2.48 times as big as that when it is incident along transverse direction (0°). Wave-current forces acting on rectangular structure are generally bigger than wave forces in the wave only condition; however, influence coefficients of incident angles on wave-current forces or wave forces are relatively close.