HOS-ocean: Open-source solver for nonlinear waves in open ocean based on High-Order Spectral method

Abstract The applicability of the High-Order Spectral Method (HOSM) as a very fast non-linear method for deterministic short-term wave prediction is discussed within this paper. The focus lies on the systematic experimental validation of the HOSM in order to identify and evaluate possible areas of application as well as limitations of use. For this purpose, irregular sea states with varying parameters such as wave steepness and underlying wave spectrum are addressed by numerical simulations and model tests in the controlled environment of a seakeeping basin. In addition, the influence of the propagation distance is discussed. For the evaluation of the accuracy of the HOSM prediction, the surface similarity parameter (SSP) is utilized, allowing a quantitative validation of the results. The results obtained are compared to linear wave prediction to discuss the pros and cons of a non-linear deterministic short-term wave prediction. In conclusion, this paper shows that the non-linear deterministic wave prediction based on HOSM leads to a substantial improvement of the prediction quality for moderate and steep irregular wave trains in terms of individual waves and prediction distance.

Download Full-text

Extreme wave statistics of random waves propagating over a 3D varying bathymetry

10.5194/egusphere-egu21-9261 ◽

2021 ◽

Author(s):

Christopher Lawrence ◽

Karsten Trulsen ◽

Odin Gramstad

Keyword(s):

Velocity Field ◽

Spectral Method ◽

Local Maximum ◽

High Order ◽

Surface Elevation ◽

Irregular Waves ◽

Extreme Wave ◽

Boussinesq Model ◽

Wave Statistics ◽

High Order Spectral Method

Non-uniform bathymetry may modify the wave statistics for both surface elevation and velocity field. Laboratory evidence reported by Trulsen et al. (2012) shows that for a relatively long unidirectional waves propagating over a sloping bottom, from deep to shallower water, there can be a local maximum of kurtosis and skewness in surface elevation near the edge of the shallower side of the slope. Recent laboratory experiments of long-crested irregular waves propagating over a shoal by Trulsen et al. (2020) reported that the kurtosis of horizontal velocity field have different behaviour from the kurtosis of surface elevation where the local maximum of kurtosis in surface elevation and horizontal velocity occur at different location. In present work, we utilize numerical simulation to study the evolution of skewness and kurtosis for irregular waves propagating over a three-dimensional varying bathymetry. Numerical simulations are based on High Order Spectral Method (HOSM) for variable depth as described in Gouin et al. (2017) for wave evolution and Variational Boussinesq model (VBM) as described in Lawrence et al. (2021) for velocity field calculation.&#160;ReferencesGOUIN, M., DUCROZET, G. & FERRANT, P. 2017 Propagation of 3D nonlinear waves over an elliptical mound with a High-Order Spectral method. Eur. J. Mech. B Fluids 63, 9&#8211;24. LAWRENCE, C., GRAMSTAD, O. & TRULSEN, K. 2021 Variational Boussinesq model for kinematics calculation of surface gravity waves over bathymetry. Wave Motion 100, 102665. TRULSEN, K., RAUST&#216;L, A., JORDE, S. & RYE, L. 2020 Extreme wave statistics of long-crested irregular waves over a shoal. J. Fluid Mech. 882, R2. TRULSEN, K., ZENG, H. & GRAMSTAD, O. 2012 Laboratory evidence of freak waves provoked by non-uniform bathymetry. Phys. Fluids 24, 097101.

Download Full-text