Numerical analysis of wave run-up characteristics on dual non-submerged vertical cylinders system

Wave run-up is an important parameter in offshore structures and ocean platforms design. A comprehensive understanding of its characteristics benefits the structural safety and design optimization. In this study, a numerical model is set up to solve the mild slope equation proposed by Berkhoff using the finite element method. The computational results of wave height distribution around the single non-submerged vertical cylinder match with the analytical solutions very well, verifying the validity of the numerical model. Subsequently, the effect of the spacing between two cylinders on wave run-up is investigated by observing the dual non-submerged vertical cylinders system. The numerical results show that the curve of wave height distribution around the upstream cylinder has a big fluctuation. However, the positions of maximum and minimum wave heights are the same as those in the single cylinder case. When the spacings are odd times of 1/4 incident wavelength, the minimum wave height decreases obviously and the secondary peak appears on the shoulder of the cylinder; when the spacings are even times of 1/4 incident wavelength, the minimum wave height obviously increases and the secondary trough appears on the shoulder of the cylinder. The curve of wave height distribution around the downstream cylinder is similar but smaller than that in the single cylinder case.