Spatio-Temporal Measurements of Water-Wave Height and Slope using Laser-Induced Fluorescence and Splines

Within the framework of this thesis an algorithm was designed, which extracts the height of water waves from a time series of along-wind surface profile images. The surface position is detected with help of thresholding and subsequently fitted on the basis of two-dimensional smooth spline fitting. As result a function of the height in space and time direction and its slope as well as its time derivative are obtained. For wind speeds of up to 10 m/s it was possible to identify the height with an accuracy of approximately 18 µm. Furthermore, a script for data evaluation was written, which computes general properties of the wave field, like the significant wave height and the mean square slope in along-wind direction, as well as the frequency spectra and the dispersion relation. Both tools were used to evaluate measurements with wind speeds from 2.5 m/s to 14 m/s performed at the Large Marseille-Luminy Wind-Wave Facility within the ASIST-campaign in June 2016. The wave field differs from pure wind waves to additional mechanically generated waves with frequencies of 0.9 Hz and 1.3 Hz.