Current velocity estimation using a lateral line probe

Freshwater ecosystems are inhabited by a vast spectrum of organisms, each with their own complex biotic-abiotic relations. Considering the management and conservation of these environments, it is necessary to understand the underlying hydrodynamic interactions to which aquatic organisms are subject. Outside of bulk flow properties such as the time-averaged velocity, it is currently difficult or impossible to obtain detailed observations of the fluid-body interaction using current measurement technology. It is in this context that the lateral line probe (LLP) has been developed. The LLP mimics the performance of flow sensing modalities present in many aquatic vertebrates. Research in the last decade has demonstrated that such devices are able to reproduce signals relevant to fish behavior and estimate the hydrodynamic stimulus response of the lateral line. However in most cases, the application of LLPs have been limited to idealized conditions, subject to rigorous calibration. In this paper we present an algorithm that allows the use of LLPs for current velocity estimation without sensor calibration. The method makes use of the fluctuations in the near-body pressure field induced by fluid-body interactions and introduces a semi-empirical resampling process based on the conservation of energy. The algorithm is calibrated using a closed flume and measurements taken using a laser Doppler anemometer. Validation of the approach is carried out by comparing results obtained with an acoustic Doppler velocimeter (ADV) in a vertical slot fishway. The mean error as compared to direct measurements with the ADV was found to be 0.11 m/s with a correlation of 0.92.