статья в журнале

En

Ocean Engineering

ISSN:00298018

2020

10.1016/j.oceaneng.2020.108043

Low-cost commercial micro-electro-mechanical system (MEMS)-based inertial motion unit is used for sea surface wave measurements. A buoy is developed based on the capacitive silicon-based accelerometer–gyroscope–magnetometer sensor with radically simplified architecture allowing a significant reduction of the buoy hull size down to 14-cm diameter and hence increased high-frequency sensitivity. The proposed buoy design is suitable for short-term manual wave measurements with minimal deployment–recovery efforts and/or experiments where knowledge of the high-frequency part of the spectrum is preferable. The buoy data is validated in a field experiment at the Black Sea stationary research platform using reference measurements of the six-wire resistive wave gauge. The strapped-down buoy measurements are transformed into the georeferenced buoy tilts and vertical acceleration using small wave slope approximation. The classical (Longuet-Higgins et al., 1961) approach is used for directional wave spectra estimation. Under 1 to 15 m/s wind speed, pure wind and mixed sea conditions, the significant wave height, wave peak period, wave direction, and spectral width are well reproduced by the buoy. The buoy geometric cut-off frequency, about 2.5 Hz, corresponding to wavelength twice the hull diameter, is at least 2.5 times better than that of commercially available buoys. The sub-peak low-frequency noise, typical for accelerometer-derived spectra, is wind-dependent and thus is clearly not the intrinsic sensor noise, but rather results from the buoy non-linear response to the waves. The detected high-frequency (4 < f < 80Hz) spectrum tail also depends on the wind speed in accord with the short-wave wind-driven wave spectrum model. The observed high-frequency sensitivity may be useful for short-wave sensing beyond the geometric cut-off frequency with MEMS-based sensors.

Buoy, Inertial motion unit, Micro-electro-mechanical system, Sea surface, Short gravity waves

2020-09-29 15:42:29