Numerical simulation of wave interaction with vertical circular cylinders of different submergences using immersed boundary method

• Model based on multiple-layer σσ-coordinate and immersed boundary method is set up.
• Model is verified for multiple classical problems of wave-structure interaction.
• Wave diffraction, wave forces and wave-induced moments on a cylinder are analyzed.

A three-dimensional numerical model has been developed to simulate wave-structure interaction over an uneven bottom. This model is an extension of the earlier multiple-layer σ-coordinate model (Lin, 2006) by including the direct-forcing immersed boundary method to deal with curved body surfaces. The model verification for free surface computation is firstly conducted. One case is regular wave diffraction over a large vertical circular cylinder. The computational results show good agreement with the analytical solution. The other is nonlinear wave interaction with a fixed floating vertical circular cylinder. The numerical results of free surface agree well with the experimental results and other numerical data found in literatures. The model verification of force and moment is done next. For solitary wave interaction with a vertical circular cylinder, the numerical results are compared with the experimental data and good agreements have been obtained for wave elevation and net wave force acting on the cylinder. For wave diffraction around a fixed submerged vertical cylinder in a finite water depth, the horizontal forces, vertical forces and moments on the structure agree well with the analytical solution and numerical results of a higher order boundary element method.