Wave directional spectrum from array measurements
Abstract
Using the method of Esteva (1976, 1977), whcih assumes that at the frequency band the waves approach from just a single "mean" wave direction, wave direction has been consistently, accurately and unambiguously evaluated as a function of frequency, from time series observations of wave elevation at a 15-gauge polygonal array, in 8 m water depth, operational at the Field Research Facility (FRF) at Duck, North CArolina, USA. It was found that, a maximum of 15 redundant estimates of wave direction has a standard deviation of less than less than4 degrees in the range 14-4 s during 1-6 February, 1994 and that swell of 10 sec came from the east. A developing sea during the time period 01-13 hours on 2 February, was due to a Northeaster, owing to which the wave direction in the wave period range 7-4 s aligned itself with the wind direction, and the significant wave height increased for 0.70 to 1.5 m. Estimates of wave direction using Esteva's method were in agreement with those obtained by the FRF using the conventional Iterative Maximum Likelihood Estimation method, which assumes that at a given frequency waves can approach simulteneously from all directions.
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