Computer vision-based measurement of wave force on the rectangular structure

Measurement of the wave force acting on the structure is normally achieved by the traditional load cells. In this study, a non-contact computer vision (CV)-based method is proposed, which can conveniently acquire the wave pressure and force without installing pressure sensors or load cell mounted on the structure. Based on the ve-locity field measured by the Optical Flow technique, the pressure field is successfully computed by solving the Poisson pressure equation, and the wave force is further determined by integrating the pressure over the surfaces of the structure. The proposed method is verified by conducting a series of laboratory experiments of wave interacting with the rectangular structure. The accuracy of the method is validated by comparing with the results measured by pressure sensors. It indicates that the CV obtained pressure and wave forces generally agree well with the sensor measured results, including the time history of wave force and the peak wave force, and the reasons for the deviation and error are also discussed. The effects of wave height and wave period on the pressure field and wave force are studied, and it is found that the Keulegan-Carpenter number is an important parameter determining the peak wave force. Finally, the limitations existed in this method are noted, including the two-dimensional simplification and air bubble effects, which need to be addressed in the future.