• Research,

LHEEA's Mini-seminar: 16/11/2017 "Reconstruction and real time prediction of ocean waves from optical measurements", Nicolas Desmars

The LHEEA organizes mini-seminars every Thursday afternoon. The next seminar will be held in the distance-learning room on 16 November at 1.45pm. Open to all!

On November 16, 2017 from 13:45 To 14:30

On November 16, 2017 from 13:45 To 14:30

This week:

Nicolas DESMARS (PhD student EMO) will present his work on "Reconstruction and real time prediction of ocean waves from optical measurements".

Abstract: "We investigate phase-resolved reconstruction algorithms and models for a deterministic prediction of ocean waves based on optically measured surface elevations. We consider a single sensor (e.g. lidar, stereo-video, etc.) mounted on an offshore structure, measuring free surface elevation at the appropriate incident direction for a given wave field and chosen target area of prediction. If assuming a uniform distribution of measurements over the viewing angles of the sensor, the density of observation points of the free surface geometrically decreases with the distance from the sensor. Additionally, a wave shadowing effect occurs, which becomes more important with small viewing angles (i.e. grazing incidence on the surface). These effects result in observations of surface elevation that are very sparsely distributed. We discuss the characteristics of a data assimilation process, which is able to retrieve fields of deterministic wave properties, such as free surface elevation, based on such a heterogeneously spread dataset. Then, a classical model based on linear wave theory is compared to the choppy wave model. The latter model is based on a Lagrangian formulation of the free surface, capable of modeling wave properties that are shown to be of importance in a proper representation of the free surface and its time evolution. Synthetic datasets from nonlinear High Order Spectral simulations are used as reference oceanic surfaces. Predicted results are analyzed over an area that evolves in time, using the theoretical amount of information assimilated during the reconstruction of the wave field."

Published on November 6, 2017 Updated on July 8, 2018