MNLS simulations of surface wave groups with directional spreading in deep and finite depth waters

Abstract We simulate focusing surface gravity wave groups with directional spreading using the modified nonlinear Schrödinger (MNLS) equation and compare results a fully-nonlinear potential flow code, OceanWave3D. alter direction characteristic wavenumber of MNLS carrier wave, to assess impact on simulation results. Both truncated (fifth-order) exact version linear dispersion operator are used for equation. The based theory quasi-determinism narrow-banded Gaussian spectrum. find that operators both perform well if: (1) aligns group propagation; (2) coincides initial spectral peak. However, simulations significantly better if does not align or coincide also finite-depth dimensionless depths ( $$k_{\text {p}}d$$ k p d ) between 1.36 5.59, incorporating depth into boundary conditions as operator, those code limitations MNLS.