A cross-platform microstructure turbulence measurement package

Abstract

Ambient turbulence in the ocean is responsible for dissipating the kinetic energy in the ocean at very small scales. Small autonomous underwater vehicles (AUVs) provide versatile mobile platforms for surveying a shallow water coastal environment at low operational costs. The platforms are uncoupled from the low frequency vibrations associated with platforms towed from surface ships. Measurement of turbulent microstructure and the associated dissipation rate using an AUV requires accommodation of the inherent vibration characteristics of a self-propelled platform. Often such vibrations are in the range of flow measurements of interest and may corrupt the data. At Florida Atlantic University, a turbulence measurement package has been developed which implements vibration isolation from the AUV platform. The sensors in the package include two shear probes, a fast response temperature probe, a fast response conductivity probe and accelerometers for monitoring vibrations. In addition, the turbulence package developed is modular and interoperable in the sense that it may be mounted on a variety of platforms in a simple robust fashion without changes to the platform. The AUV platforms used thus far include the Ocean Explorer vehicle at Florida Atlantic University and the Autosub at the Southampton Oceanography Center. These vehicles vary in size from 2 meters long and under 200 kg for the OEX to over 7 meters long and over 1500 kg for the Autosub. The design of the turbulence package and results from implementation aboard these very different autonomous underwater vehicles are described.