Free-Surface Measurements in a Tow Tank Using LiDAR

Light Detection and Ranging, or LiDAR, is a remote sensing technique that can be utilized to collect topographic data. These systems have been used extensively to measure open ocean and ship generated waves. Recently LiDAR systems have been used to measure the transom wave of the R/V Athena I and ambient ocean waves. This work has primarily focused on providing the time averaged, and spectral content of the wave field, by scanning the laser to measure wave profiles evolving in time. This paper describes recent efforts to utilize LIDAR systems to measure free-surface elevations in laboratory tow tanks. LiDAR measurements are limited to the white-water breaking regions of the flow, due to the limited strength of the signal return from non-breaking regions. In extending LiDAR measurements to a laboratory tow tank environment the lack of surface roughness and hence the lack of surface light scatterers needed to be addressed. A number of laboratory measurement applications will be described including a tow tank measurement similar to the R/V Athena I effort, and also measurement of regular and irregular breaking waves.