A locally nonlinear interpretation of PUV measurements

A time domain method is presented for analyzing simultaneous measurements o f pressure and the horizontal components of velocity obtained beneath irreg ular multidirectional wave fields. This new method differs from the usual l inear directional analyses applied to PUV data in two important aspects. Fi rst, the essential nonlinearity of the measured waves is not sacrificed to achieve a solution. Therefore, predictions of sea surface elevation and dir ectional kinematics throughout the water column accurately portray the actu al nonlinear character of the waves. Second, the analysis method is 'local' in that it can be applied to segments of PUV time series much shorter than an individual wave, The viability of the locally nonlinear methodology dev eloped in this paper is proven by demonstrating agreement with higher-order theoretical steady waves. predictions of sea surface elevation and wave ki nematics are also made using actual measurements from PUV instruments at tw o ocean sites off the west coast of the United States. (C) 1999 Elsevier Sc ience B.V. All rights reserved.