Development, testing and demonstration of a portable submersible miniature particle imaging velocimetry device

Abstract

A portable underwater particle image velocimetry (PIV) device has been developed, tested and demonstrated. The underwater PIV uses a 532 nm battery-powered 90 mW continuous laser. The laser beam is pulsed via a camera-synchronized chopper wheel. Images were recorded using a 1 megapixel black and white 10-bit CCD battery-powered camera controlled via a PCMCIA frame grabber card connected to a laptop computer. The system was validated against a standard laboratory PIV for average velocities up to 15 cm s−1 downstream from a 1.6 cm circular cylinder. The average vorticities calculated between the two systems were similar with a maximum difference of 3.6%. The average velocities were also similar with the largest difference occurring at the slowest flow recorded (difference of 0.5 cm s−1), resulting in a 9.4% difference. The maximum eddy size was comparable between the two systems with an average error of 4%. The system was field tested in the Huron River, Michigan downstream from a 1.2 cm diameter submerged limb. Mean velocities and standard deviations were comparable to acoustic Doppler velocimeter data. This paper presents the first published subsurface PIV data from a fluvial environment, demonstrating potential applications for a number of ecological and geomorphological studies.