The Barnacle: A low-cost marine turbulence sensor

Abstract

The Barnacle is a new form of marine sensor, which offers a low-cost alternative to the Acoustic Doppler Velocimeter (ADV) for turbulence measurements in oceanographic applications, including tidal power sites. This new device measures flow velocity from pressure differences between slanted faces, and is estimated to cost five to ten times less than an ADV. The Barnacle is of interest to tidal turbine developers because accurate quantification of the unsteady inflow is vital for determining fatigue loads.In this work, results are presented from a benchmarking campaign against an ADV in the Strangford Narrows (County Down, Northern Ireland). When the Vector performs optimally (i.e., with minimal noise), good agreement is seen between the Barnacle and the ADV in the streamwise direction: mean flow measurements are typically within 5%.The Barnacle is less susceptible to random noise than the ADV: the noise floor is up to two decades lower. Good agreement is observed in unsteady flow measurements, and the streamwise turbulence intensity estimates from the two devices are consistently within 3 percentage points.Overall, the novel approach outlined here offers a robust, low-cost alternative to traditional techniques for oceanographic turbulence measurements, in particular directional flows and tidal power sites.