Image-clustering analysis of the wave-structure interaction processes under breaking and non-breaking waves

This contribution presents the effectiveness and the potentialities of a consolidated technique—the video-cluster analysis—to the study of turbulent flow and breaking waves, in order to demonstrate its suitability as a low-cost, non-intrusive method to derive quantitative key parameters describing the wave-structure interaction processes at coastal defense structures. For this purpose, a new methodology, consisting of a series of pre- and post-processing techniques developed to optimize the automatic detection of clusters in video imagery, was designed to process the video-records of experiments of wave run-up and wave overtopping at sea-dikes subjected to irregular waves. The results of the cluster analysis were elaborated to reconstruct the instantaneous profiles of the free-surface elevations across the structure crest and derive simultaneous information on overtopping volumes, discharges, depths, and velocities and to get spatial-time maps of the concentration of the air entrapped in the liquid phase. The accuracy of the methodology is demonstrated by comparing the quantities derived from the cluster analysis to laboratory measurements performed with resistive gauges and acoustic Doppler profilers. The novelty of the work is either represented by the results of the application of the cluster-analysis and by the procedures of optimizations, whose ensemble may establish a best practice and represent a guideline for other applications.