Surface wave heights from pressure records

Abstract

Various studies in the past have considered the ability of the linear and other wave theories to predict surface wave conditions from near-bottom pressure records accurately. This paper is an extension of such work. In deterministic terms, considerations involve the ability of the linear and second-order cnoidal wave theories to predict accurately surface wave heights from individual, near-bottom, total pressure head ranges. In stochastic terms, the fidelity of the Gaussian random process in making predictions of a surface spectrum will be assessed. Both field and laboratory data are employed in this work. The field data were taken in the ocean off Honolulu, Hawaii, in 11.3 m of water, and involved swell with periods of from 12 to 17 sec and heights to 3.2 m. The laboratory data were taken for water depths of 2.9 and 3.5 m in the large Wave Research Facility of Oregon State University, Corvallis, Oregon, and involved periods of from 2 to 6 sec and heights to 1.5 m. It was found that the cnoidal wave theory is slightly superior to the linear theory in predicting surface heights for the ocean data. As found by other investigators, the linear theory was found to underestimate surface wave heights for low frequencies and overestimate them for high frequencies. It was found that the Gaussian random process model provided a theoretical surface spectrum that corresponded closely to that measured over a reasonable frequency band.