Publication Date:
1982-10-01
Description:
Displacements of wind waves in the laboratory were measured with a laser displacement gauge, a recently developed, optical, non-intrusive sensor, which avoids the meniscus effects that severely limit the frequency response of conventional thin-wire gauges. The new gauge is a digital device, which has a maximum frequency response of 25 kHz. Its spatial resolution, which depends on the field of view, is typically 0016 cm for a 4 cm field of view. The wind-wave displacements were measured at several fetches for three wind speeds. Wave-variance spectra derived from these measurements indicate the presence of a quasi-equilibrium spectrum in the capillary-wave regime. The quasi-equilibrium spectrum follows an f-7/3 power law that has been predicted on dimensional grounds. The spectral density increases with increasing wind speed from 4 to 10 m/s but is independent of the fetch from 3 to 5 m. In addition, the capillary-wave spectrum is practically unchanged when a relatively long but -low-amplitude mechanical wave is superposed onto the windgenerated waves. © 1982, Cambridge University Press. All rights reserved.
Print ISSN:
0022-1120
Electronic ISSN:
1469-7645
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
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