Near surface irregular wave kinematics

Abstract

Presents measurements and analysis of near surface kinematics for two irregular sea states generated in the offshore basin at the Danish Hydraulic Institute. A triaxial ultrasonic current meter (Minilab SD 12) was used. The wave kinematics were derived from the measured surface deviation (using interpolation). Crossing analysis of the theoretical and measured velocity series, plus spectral analyses of measured and calculated velocities are presented. Results suggest that second order irregular wave theory predicts satisfactorily the velocities beneath the wave troughs. Recommends conditions for using extrapolation or coordinate stretching, for estimating velocity amplitudes under the crests. (C.J.U.)