Numerical Study of the Effect of Submerged Vertical Breakwater Dimension on Wave Hydrodynamics and Vortex Generation

The effect of submerged vertical breakwater dimension on wave hydrodynamics and vortex generation around the breakwater is investigated with numerical modeling via two dimensionless parameters: the breakwater dimensionless submergence depth (a/H_i; a-the breakwater depth of submergence) and the Keulegan-Carpenter number (KC = H_iπ/L_bw; H_i-incident wave-height and L_bw-breakwater width). In the numerical model, Reynolds Averaged Navier-Stokes (RANS) equations with a standard k-ε turbulence closure model were implemented; the free surface was traced using the VOF method. A total of 10 different simulations with different KC number and breakwater submergence depth were conducted for this study. The results revealed that the transmission coefficient increases with increasing a/H_i and KC number, but that the effect of the KC number is not linear like the relation to a/H_i. For the waves modeled, the transmission coefficient increases dramatically with increasing the KC number until the KC number reaches a critical value, this critical value is observed when breakwater width is equal to a quarter of wavelength. This gives a hint in design of breakwater width. Turbulence intensity decreases with increasing a/H_i and KC on the seaside of the breakwater while it increases especially near the bed on the leeside of the breakwater; this can increase scour risk on the leeside of the breakwater. The optimum a/H_i for both, high-energy dissipation rate and low risk of scour tends to 3.5 for KC ≈ 1.0.