Fully Nonlinear Wave-body Interactions With Fully Submerged Dual Cylinders

A 2-dimensional fully nonlinear numerical wave tank (NWT) is developed based on the potential theory, Mixed EulerianLagrangian (MEL) time marching scheme and boundary element method (BEM). Wave deformation and wave forces on submerged single and dual cylinders are investigated using the NWT. The computed mean, 1st , 2ndand 3rd-order wave forces on a single submerged cylinder are compared with those of Chaplin’s experiment, Ogilvie’s 2nd-order theory, and another nonlinear computation called high-order spectral method. The computed potential-based mean, 2nd and 3rd harmonic forces agree well with lab measurement, but there exists noticeable discrepancy in the 1st-order wave forces as the KC number increases, which can be attributed to viscous effects (clockwise circulation around the body). An independently developed 2-D viscous NWT confirmed the experimental observation. The NWT simulations for submerged dual cylinders show that the interaction effects can be significant when the gap is small. In particular, the higher harmonic forces on the rear cylinder can be greatly increased due to already deformed incident waves by the front cylinder. The potential NWT results for dual cylinders are also compared with those including viscous effects.