Measurement of Water Surface Particle Kinematics Using a Motion Tracking System

Water particle motions on the wave surface are of interest to the designer for various applications that require quantification of particle kinematics. Difficulties in predicting these kinematics lead to other alternatives such as measurements in model tests. The modelled waves themselves as generated in facilities may also be of interest. Devices to measure particle motion adopted from fluid flow measurement equipment, are generally not well suited to measure particle kinematics because of limitations in their response or intrusiveness within the wave field. This paper discusses the use of a motion tracking device to measure wave surface particle kinematics. Small spheres floating on the wave surface are tracked using an optical tracking device and their position is determined as a function of time using monitoring cameras. Tests were carried out in a series of regular and irregular waves. Measured kinematics are compared and discussed in relation to those predicted by wave theories.