Jaak Monbaliu

Comparison of wave-current interaction formulation using the POLCOMS-WAM wave-current model

Ocean processes do not take place in isolation but interact with one another to form a complex system. This paper focuses on these processes by using and developing the POLCOMS-WAM model. The Stokes’ drift and radiation stress effect on currents have been included, following state of the art formulations. The system is evaluated in the NW Mediterranean and the Irish Sea. Due to oceanographic properties of the Catalan coast, currents are typically less than 20 cm/s and therefore the modification of waves due to the effect of currents is minimal. However, the wave induced currents, mainly caused by enhanced wind drag due to waves, produce a current of about the same magnitude as the ambient one and thus become an important source of mass transport. For the Irish Sea an improvement of storm surge modelling by considering a wave modified wind stress is presented.

Wind generated rogue waves in an annular wave flume

We investigate experimentally the statistical properties of a wind-generated wave field and the spontaneous formation of rogue waves in an annular flume. Unlike many experiments on rogue waves where waves are mechanically generated, here the wave field is forced naturally by wind as it is in the ocean. What is unique about the present experiment is that the annular geometry of the tank makes waves propagating circularly in an unlimited-fetch condition. Within this peculiar framework, we discuss the temporal evolution of the statistical properties of the surface elevation. We show that rogue waves and heavy-tail statistics may develop naturally during the growth of the waves just before the wave height reaches a stationary condition. Our results shed new light on the formation of rogue waves in a natural environment.

Non-Gaussian Properties of Shallow Water Waves in Crossing Seas

The Kadomtsev–Petviashvili equation, an extension of the Korteweg–de Vries equation in two horizontal dimensions, is here used to study the statistical properties of random shallow water waves in constant depth for crossing sea states. Numerical simulations indicate that the interaction of two crossing wave trains generates steep and high amplitude peaks, thus enhancing the deviation of the surface elevation from the Gaussian statistics. The analysis of the skewness and the kurtosis shows that the statistical properties depend on the angle between the two wave trains.