Session: 06-03-06 Fluid-Structure, Multi-body and Wave-body Interaction VI

Paper Number: 124743

124743 - Correlation Between the Observed White Capping Area and the Measured Spectral Energy Dissipation in Physical Breaking Experiments 

Physical experiments have been done in the Coastal & Ocean Basin (COB) in Ostend (Belgium) to better understand the energy dissipation processes due to breaking. During the experimental campaign, JONSWAP spectra with four distinct peak steepness’s (k_pA_s = 0.10, 0.15, 0.2, and 0.25) were generated for two different peak periods (T_p = 0.8, and 1 s) in deep water conditions (h = 1.4 m). Both long- and short-crested waves are considered. For the short-crested cases, a cos2s spreading function is applied to the unidirectional spectrum with three different spreading parameters (s = 25, 10, and 3). The resulting sea states were monitored in two adjacent zones of 6 m x 6 m in two complementary ways. In the one zone, evenly distributed wave probes measured how the energy spectrum evolves over the length of the basin. It was observed that when moving away from the wavemaker, the tail of the spectrum first becomes heavier until breaking occurs. After breaking the tail is lighter, suggesting that the energy dissipation happens at the higher frequencies. Above the other observation zone, a video camera was installed to film the water surface and detect white capping events. A machine-learning algorithm is trained to automatically determine the average white capping area in different regions of the visual observation zone. In order to combine the spectral information from the wave gauges with the visual information from the camera, the two zones were interchanged before repeating the experiments with exact the same sea states. This allows to correlate the detected white caping area along the 12 m x 6 m zone of interest to the measured energy dissipation due to the breaking events. Furthermore, it provides valuable data to calibrate and validate multidirectional breaking models.  

Presenting Author: Tim Aertsens KU Leuven & The University of Melbourne

Presenting Author Biography: Tim Aertsens did both his Bachelor’s in Engineering Science and his Master’s in Civil Engineering at the KU Leuven in Belgium. During his Master’s degree, he did an exchange of one semester to Polytechnique Montreal. After his graduation in 2021, he was granted a Strategic Basic Research Fellowship by The Research Foundation – Flanders (FWO) for his PhD project at KU Leuven on the new Coastal & Ocean Basin. He decided to spend one year of this PhD at The University of Melbourne under the guidance of Prof. Toffoli in order to obtain a joint degree.

Authors:

Tim Aertsens KU Leuven & The University of Melbourne
Roberto De Lima Hernandez KU Leuven
Hilton Tnunay KU Leuven
Maarten Vergauwen KU Leuven
Jaak Monbaliu KU Leuven
Alessandro Toffoli The University of Melbourne