Spatio-Temporal Resolution of Different Flow Measurement Techniques for Marine Renewable Energy Applications

Marine hydrokinetic (MHK) energy conversion devices are subject to a wide range of turbulent scales, either due to upstream bathymetry, obstacles and waves, or from wakes of upstream devices in array configurations. The commonly used, robust Acoustic Doppler Current Profilers (ADCP) are well suited for long term flow measurements in the marine environment, but are limited to low sampling rates due to their operational principle. The resulting temporal and spatial resolution is insufficient to measure all turbulence scales of interest to the device, e.g., "blade-scale turbulence." The present study systematically characterizes the spatial and temporal resolution of ADCP and Acoustic Doppler Velocimetry (ADV). Simulations were used to quantitatively investigate the flow scales that each of the instruments can resolve in low and high turbulence intensity flows. For comparison, measurements were conducted at the UNH Tidal Energy Test Site in Great Bay Estuary at General Sullivan Bridge. The purpose of the study is to supply data for mathematical modeling to improve predictions from ADCP measurements, which can help lead to higher-fidelity energy resource assessment and more accurate device evaluation, including wake measurements.