Validation and practical application of nonlinear wave decomposition methods for irregular waves

• Published in: Coastal engineering (Amsterdam) 2023-08, Vol.183, p.104311, Article 104311
• Main Authors: de Ridder, Menno P., Kramer, Jan, den Bieman, Joost P., Wenneker, Ivo
• Format: Article
• Language: English
• Subjects: Automated video analysis; Nonlinear wave decomposition; Physical model tests
• ISSN: 0378-3839
• DOI: 10.1016/j.coastaleng.2023.104311

When performing physical or numerical experiments in a wave flume, it is important to distinguish between the incident and reflected wave components. Recently wave separation methods including nonlinear effects were presented which can be applied for a large range of conditions and reduces the error in the wave separation. However, these nonlinear methods also result in a complex system of equations and require more wave gauges. In this work, physical model experiments with a high spatial resolution of wave gauges were carried out to validate different wave separation methods. All tests were analysed with a Linear method, the nonlinear method described in Eldrup and Lykke Andersen (2019) (ELA method) and a Modified ELA method. In this Modified ELA method, the model complexity depends only on the condition number of the phase difference matrix making the accuracy less dependent on wave gauge positions and noise. The results show that both Nonlinear methods are always preferred over the Linear method. A detailed analysis of the number of wave gauges shows that for the same distance between first and last gauge, 6 to 8 wave gauges are required for a converged solution independently of the wave gauge position. In an ideal situation – with an ideal number of wave gauges and ideal spacing between them – the ELA and Modified ELA methods should give nearly identical results. However, for the non-ideal conditions encountered in practice, the Modified ELA is shown to be more robust. •An existing nonlinear wave separation method is extended and improved.•Validation of wave separation methods is performed using physical model data.•A convergence study is performed using large amounts of wave gauges.•Practical guidelines are derived for the number of wave gauges.•A Nonlinear separation method is always preferred over a Linear method.