The two-dimensional problems concerning the interaction of linear water waves with cylinders of arbitrary shape in two-layer deep water are investigated by use of the Boundary Integral Equation Method （BIEM）. Simpler new expressions for the Green functions are derived, and verified by comparison of results obtained by BIEM with those by an analytical method. Examined are the radiation and scattering of linear waves by two typical configurations of cylinders in two- layer deep water. Hydrodynamic behaviors including hydrodynamic coefficients, wave forces, reflection and transmission coef- ficients and energies are analyzed in detail, and some imeresting physical phenomena are observed.
Numerical simulations of freak wave generation are studied in random oceanic sea states described by JONSWAP spectrum. The evolution of initial random wave trains is namerically carried out within the framework of the modified fourorder nonlinear Schroedinger equation （mNLSE）, and some involved influence factors are also discussed. Results show that if the sideband instability is satisfied, a random wave train may evolve into a freak wave train, and simultaneously the setting of the Phillips paranleter and enhancement coefficient of JONSWAP spectrum and initial random phases is very important for the formation of freak waves. The way to increase the generation efficiency of freak waves thsough changing the involved parameters is also presented.
