Development of an in situ underwater particle image velocimetry (UWPIV) system

A low-cost self-contained underwater particle image velocimetry (UWPIV) system has been developed to measure small-scale turbulent flow structures in situ. The UWPIV employs a compact continuous-wave laser and an optical scanner to deliver a light sheet that illuminates naturally occurring particles. Particle images are taken by a CCD camera along with an ultra-compact PC. The nontethered and compact design can be fit in two small underwater housings with all components powered by batteries: an ideal design for a variety of in situ deployments. The system has been field-tested in the coastal zone of Lake Michigan. Turbulent flow structures of the wave-current bottom boundary layer are measured right above the nearshore lakebed, which is densely covered by quagga mussels (Dreissena bugensis). Vertical profiles of mean velocity, Reynolds stresses, dissipation rate of the turbulent kinetic energy, turbulent viscosity, plankton particle concentration, and the turbulent flux of particles are presented and discussed.