Implementation of Higher Order Spectral method for nonlinear wave propagation in OpenFOAM

Higher Order Spectral (HOS) method for nonlinear surface wave propagation is implemented in OpenFOAM. HOS is a pseudo–spectral method for solving nonlinear free surface boundary conditions up to arbitrary order of nonlinearity. Time relaxation scheme is used to enable initialization using linear solution. Linear initialization enables propagation of arbitrary input spectrum. Use of Fast Fourier Transform (FFT) reduces CPU time, making this method favourable for coupling with CFD. The method is implemented as a wave theory in the Naval Hydro pack, using existing FFT and time integration algorithms. Implemented code is validated on both regular and irregular wave propagation. Development of higher modes for a regular wave initialized with linear solution is compared with the work by Dommermuth. Nonlinear propagation of irregular input spectra is compared with viscous simulation results by Lupieri et al. Finally, development of Benjamin–Feir instability on regular wave propagation is observed.