Measuring shallow water waves with pressure sensors
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Authors
Goncalo, Vitor Manuel Henriques
Subjects
Wave staff
Pressure sensor
Water particle velocity
Orthogonal components
Bernoulli equation
Flowmeters
Pressure sensor
Water particle velocity
Orthogonal components
Bernoulli equation
Flowmeters
Advisors
Thornton, Edward B.
Date of Issue
1978-09
Date
September 1978
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
For two locations within the surf zone sea surface elevations were observed using a wave staff and a pressure sensor while simultaneously the two horizontal orthogonal components, u and v, of water particle velocity were measured.
Surface elevations derived from pressure sensors are lower, mainly in the region of the crest, compared with the same surface elevations measured with wave gages. Pressure records are more smoothed than wave gage records, and the energy computed for waves measured with a pressure sensor is consistently smaller than for waves measured with a wave gage.
Methods for converting pressure to surface elevation are given which include the non-linear velocity term (u2+v2) which is usually neglected in the Bernoulli equation. Two techniques are proposed to include this term: 1) flowmeters are used to measure u and v, and 2) the Bernoulli term is derived by determining the velocities by convolving the pressure records using a weighting function determined from shallow water theory.
The first technique gave improvements on the order of 3.4% to 7.8% of the total variance of the wave gage spectrum, whereas the second technique gave improvements on the order of 3.1% to 9.7%. The improvements in both cases are approximately the same, with the second technique having the advantage of requiring only a pressure transducer.
Type
Thesis
Description
Series/Report No
Department
Meteorology and Oceanography
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
Funder
Format
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
Copyright is reserved by the copyright owner