Numerical study on the effects of uneven bottom topography on freak waves

A numerical model is built by using an improved VOF method coupled with an incompressible Navier–Stokes solver. Exploiting the model, the freak wave formation due to the dispersive focusing mechanism is investigated numerically without uneven bottoms and in presence of uneven bottoms. During the freak wave transformation over an uneven bottom in finite water, combined effects of shoaling, refraction and reflection can modify the external characteristics of freak waves, and also can complicate the energy transfers. Furthermore, wavelet analysis method is adopted to analyze the behavior of the instantaneous energy structure of freak waves. It is found that when the bottoms vary in height, the external characteristic parameters and high frequency energy show a similar trend, but the value may be quite different due to the difference in local characteristic of the bottom.

► We model the freak wave formation without and in presence of uneven bottoms. ► We analyze effects of uneven bottoms on external characteristics of freak waves. ► We analyze effects of uneven bottoms on internal energy structure of freak waves.