19 June 2001
DETECTION OF SURFZONE WAVE BREAKING WITH
COMPARISONS TO IN-SITU VOID FRACTION MEASUREMENTS
K. T. Holland
M. Su R. E. Burge
Naval Research Laboratory
Stennis Space Center, MS 39529-5004
During both Sandy Duck 97 and Duck 99 Experiments at Duck, SC we mounted a color video camera on the top of the CERC FRF tower (42rn in height). The field of view of this video mainly covers the near-shore zone from the beach to about 500m offshore, where our three (Sandy Duck 97) and five (Duck 99) void fraction arrays were deployed. In this paper, we shall present some results from the analysis of these video images taken during windy conditions when many breaking waves were observed, and also during low wind conditions when the low tide caused many swells to break near the surfzone.
The time-lapsed large-area average over 5 to 10 minutes of these video images give clear zonal probability of wave breaking. On the other hand, variations of image intensity over a small area (averaging over a few pixels) gives the temporal characteristics of progressive breaking waves over the surfzone. Some correlation between the statistical video image intensity with those of the in-situ void fraction measurements obtained by conutcivity-type gauges will also be made.
Sponsored by the Office of Naval Research.
Abstract OS42D-09 in the Amer. Geophys. Union Spring Meeting, Boston, 1999.
Presented in June 1999.