Mapping Breaking Ocean Waves using Novel LIDAR Equipment

Research output: Book/anthology/dissertation/reportPh.D. thesis

Traditionally, the modeling of ocean wave forces acting on offshore structures, such as oil platforms or wind turbines, has been conducted using the frequency spectra of waves. These spectra are created using statistics from previous experimental campaigns, depending on the area of interest. In recent years, evidence of previously unobserved events has come to light. In other words, observations of multiple extreme breaking ocean waves have been made in areas such as the North Sea, which does not correspond with the current spectrum of the area. It is thus of great interest to monitor and measure these events in order for the creation or update of the contemporary wave models used to design offshore structures. However, the task of mapping such extreme breaking events is difficult due to the physical properties of the waves, specifically whether or not they are breaking waves. Present day mapping systems rely on theoretical values to determine these characteristics of waves. A solution to this problem is to create a system in which it is possible to map the breaking of waves. It is the focus of this dissertation to explore and develop such a system, which will enable the possibility of creating a database which will allow for future improvements of the contemporary statistics and frequency spectras.

This dissertation describes the features of such a system, which enables the mapping of breaking ocean waves by utilizing a novel optic system. The system contains a LIDAR and three cameras, one visible and two infrared. This is done in multiple steps, which in the end allows for the creation of a wave database of future storms. The initial part is a brief state-of-the-art review of the knowledge of the mapping of breaking ocean waves and what contemporary equipment is currently lacking in pursuing this objective. The contribution to the field by this author is given as the second part, with the first chapters containing the initial setup of the mapping system, allowing for the analysis of experimental full-scale data and comparison of different systems. This is done through a comprehensive description of the method of post analyzing the raw data, combined with statistical calculations on both RADAR and LIDAR data. The following chapter enables the possibility of not only mapping ocean waves, but also concluding if a wave is breaking using only the raw data and the system. Such a result is given by utilizing the fusion of data between multiple data-collection sources. This is obtained through a new method denoted the Breaking Index method, that determines at what time in a data set the onset of breaking occurs. Simultaneously, a 3-D mapping of an breaking ocean wave is depicted in the end.
Translated title of the contributionMåling af brydende bølger ved brug af moderne LIDAR udstyr
Original languageEnglish
Number of pages181
Publication statusPublished - 30 Nov 2020

    Research areas

  • LIDAR, Camera, Data fusion, Breaking ocean waves

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