VIDEO-BASED PARTICLE IMAGE VELOCIMETRY

PURPOSE

Particle Image Velocimetry (PIV) is a nonobtrusive remote sensing technique to extract (in this case) spatial dense surface currents. The beneifts of PIV are the use with which large data sets can be extracted from remote video imagery. Unfortunately, in the capacity that is used in my studies, PIV yeilds only the surface flow field. My past uses of PIV have been for swash and surf zone field data of which some is shown below. Collecting data in the swash zone of natural and laboratory beaches is difficult due to the high energy, turbulence-ridden shallow flows. PIV has been succesfully used to extract surface currents on beaches in Duck, NC (FIGURE 1).

FIGURE 1. Bathymetry in the swash zone at Duck, NC on OCT 10, 1997 and instanatenous PIV surface current vectors.

In a recent paper in collaboration with Dr. Farquharson, we compared the PIV technique with surface currents derived from doppler shift radar data (FIGURE 2). The data from the 2 remote methodlogies shows much similarity with some appraent differences within the surf zone where PIV can have difficulties when sufficient image texture is lacking.

FIGURE2. Comparison between PIV (black) and radar (gray) radial velocity components acorss the surf and swash zones at Scripps Beach in La Jolla, CA during SWASHX Experiment. Cross-shore positions are roughly from the mean waterline at this time and inrease offshore.

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