I-Spar Buoy: Design of a Lightweight Shallow Water Air-Sea Measurement Platform
Abstract
An Inner-shelf SPAR buoy (I-SPAR) for measuring atmospheric fluxes was developed for use in 7-20 m water depth as part of the ONR Coastal Land Air Sea Interaction (CLASI) effort. The design requirements are: 1) measurements obtained above the wave boundary layer (>4 m above sea level), 2) lightweight (< 100 kg), 3) dynamically stable, 4) modular for small boat transportation and deployment, and 5) able to acquire data for two months. The designed I-SPAR buoy has a 9 and 11 m length based on water depth and weighs 92 kg. The I-SPAR has an in-line configuration to reduce asymmetric wind drag. Atmospheric fluxes are estimated using a standard eddy-covariance, moving-platform technique that requires a fast-sampling sonic anemometer and inertial motion unit (IMU) to remove buoy motions and provide measurements in a geographic coordinate frame. The technique is modified by using a data-fused, Kalman filter IMU output. The I-SPAR is built with lightweight, high-strength carbon fiber tubes that are interconnected. The I-SPAR will follow low-frequency swell, where high-frequency wind waves are filtered out with a bottom damping plate. It is also designed for a maximum static tilt of 25 deg and a dynamic roll of 5.6 deg when exposed to a 15 m/s wind using vertical fins. A collocated solar-powered battery float will provide continuous power at a 50% duty cycle and includes an iridium modem for transmitting bulk statistics, including fluxes as well as providing a safety watch circle.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2020
- Accession Number
- AD1126824
Entities
People
- Vincent D. Iii Chamberlain
Organizations
- Naval Postgraduate School