Laboratory Measurements from a UUV-Mounted Barnacle Turbulence Probe

The Barnacle is a new form of marine turbulence sensor, which has been shown to work as well as, or better than, acoustic devices when rigidly-mounted. In order to undertake more ambitious oceanographic measurements, it needs to be mounted on an Unmanned Underwater Vehicle (UUV). This paper aims to quantify two challenges associated with mounting the Barnacle on a UUV. First, the Barnacle relies on pressure measurements from five faces at different angles to each other. If mounted in the vicinity of another, larger object, these pressure measurements will be distorted. This distortion must be quantified, so that steps can be taken to mitigate it or incorporate it into the velocity calibration process. Second, changes in ambient temperature will cause drift in the pressure transducers used. The Barnacle has inbuilt temperature monitoring, and so an algorithm is required to use this temperature data to remove error from the velocity measurements. In this work, a Barnacle probe was mounted on a mock-up of an ecoSUBm5 nosecone and the influence of the nosecone on the Barnacle calibration was measured at different displacements. It is shown that the Barnacle needs to be one UUV nosecone diameter upstream to avoid the errors becoming large. Furthermore, a rolling regression algorithm is shown to remove errors due to temperature changes. This new understanding paves the way for further trials with the Barnacle mounted on a UUV.