Versatile image-based measurements of granular flows and water wave propagation in experiments of tsunamis generated by landslides

摘要

Landslides falling into water bodies can generate destructive waves, which can be classified as tsunamis. An experimental facility to study this phenomenon has been set up. It consists of a landslide generator releasing gravel at high-speed into a wave basin. A non-intrusive system has been designed ad-hoc to be able to measure the high velocity and the geometry of the landslide as well as the generated waves characteristics. The measurement system employs the treatment of images captured by a high-speed camera which records the launched granular material illuminated by a laser sheet. A grid of laser sheets marks the basin water surface. The water has been filled by a small amount of kaolin to properly reflect the laser light at water surface. Thus, by filming with high definition cameras the perturbed water surface and successively processing the resulting images, it has been possible to measure the generated waves. The measurement framework employs a versatile camera calibration technique which allows accurate measurements in presence of: (1) high lens distortions; (2) pronounced non-parallelism condition between camera sensor and plane of measurement coincident with the laser sheet. The maximum resolution of the measurement tool is 0.01 mm, while the maximum uncertainty due to systematic error has been estimated to be 15% for the worst-case scenario. This work improves the suitability of image-based measuring systems in granular flows and free surface hydraulics experiments.