Numerical investigation of hydrodynamic characteristics for flow past a square cylinder due to combined wave-current effect

This paper conducts a thorough numerical investigation into the three-dimensional hydrodynamic interactions of wave-current flow with a square cylinder. Utilizing the open-source computational fluid dynamics modeling tool, the study considers variations in the Keulegan-Carpenter (KC) number, wave-current parameter ( U-cw = U-c/U-m) (U-c and U-m are the maximum velocities of current and waves), and blockage ratio ( D/L-y) (D and L-y is the one side of the pier and width of the domain, respectively). The CFD model employs the Reynolds-averaged Navier-Stokes equations with the k-omega turbulence model and the level-set method to simulate the complex movement of the free surface. Validated against existing experimental data, the model is then used to analyze the influence of blockage ratios, KC numbers, and combined wave-current effects on hydrodynamic characteristics. Key findings include an increasing drag coefficient (C-D) trend with higher blockage ratios. At the same time, under constant KC numbers, an increase in the current velocity (U-cw) results in higher C-D. Conversely, C-D decreases with an increase in KC number under fixed blockage ratio conditions. The coefficient of inertia (C-M) consistently rises with blockage ratios for a fixed KC number, and an increase in KC number corresponds to higher values of C-M. However, an increase in U-cw, with a constant blockage ratio and KC number, decreases C-M. The study also highlights that increasing blockage ratios shift the skewness of combined wave-current forces in a more positive direction, and kurtosis indicates a transition from a low-tailed to a high-tailed distribution. This study also offers insightful information on the Q-criteria and vorticity contours.