Abstract:

The breaking process of water waves has an important implication on oil dispersion in coastal waters. This study investigates the chaotic behavior of breaking waves by laboratory experiments and numerical modeling. Repeated laboratory runs with different initial velocity perturbations show that the wave profile before the wave breaks can be accurately reproduced, but the subsequent breaking process varies among runs, indicating the lack of repeatability of breaking waves in reality. Numerical simulations based on the Smoothed Particle Hydrodynamics method are further carried out to examine the repeatability of wave breaking process. Consistent with the laboratory observation, multiple numerical simulations with variations in initial conditions present highly repeatable velocity field and free surface profile in the potential flow region but considerable variation at the breaking and post-breaking processes. Comparison also shows that 3D vortex structures induced by breaking waves are different among cases. Analysis of particle trajectory reveals that there is a similar trajectory thus a minor trajectory divergence among particles that are initially located at the pre-breaking region and the flume bottom, which are not directly impacted by the breaking process. However, a much more significant particle trajectory divergence is observed among particles that are initially located at the wave-splash region and the post-breaking region. The rate of divergence of particle trajectory under breaking waves is further examined by computing the Lyapunov exponent, a widely used indicator of chaos. This study reveals that different initial velocity perturbations lead to variations of near-surface velocity at the onset of wave breaking, which eventually cause the development of drastically different breaking wave jets and splashes. Therefore, the process of wave breaking, like many other dynamic processes in nature, exhibits a chaotic behavior.

Suggested Citation:

Zhangping Wei, Cheng Li, Robert A. Dalrymple, Morteza Derakhti,Joseph Katz. 2018. Study of chaotic behavior of breaking waves by laboratory experiments and numerical simulation. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N70P0XH6

Publications:

Wei, Z., Li, C., Dalrymple, R. A., Derakhti, M., & Katz, J. (2018). Chaos in breaking waves. Coastal Engineering, 140, 272–291. doi:10.1016/j.coastaleng.2018.08.001

Purpose:

To investigate the chaotic behaviors of breaking waves, which have important implications on oil dispersion in coastal waters.

Data Parameters and Units:

The SI system was used in the work.

Methods:

Numerical work based on the smoothed particle hydrodynamics method, the specific code used in this work is GPUSPH (www.gpusph.org) Numerical work team: Zhangping Wei, Robert A. Dalrymple, Morteza Derakhti Laboratory experiment on repeated runs of breaking wave experiments Lab work team: Cheng Li, Joseph Katz

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