Spatial characterization of underwater turbine wakes using Three-dimensional three-component (3D3C) velocity measurements

A growing interest in underwater turbines (using tidal, river, and marine currents among others) has been observed during the last few years. A fundamental understanding of the turbulent flow around underwater turbines is crucial to predicting the potential effects of these structures on the local morphology, water flow, and power available in the current. The flow structure downstream of a turbine are inherently complex in that it is both unsteady and three dimensional. For this reason, a measurement technique that captures the full volumetric three-dimensional velocity field is advantageous for analyzing the complexity of the flow. In this study, a miniature horizontal axis 3-blade underwater turbine, aligned in the direction of the mean flow, was placed in a water flume at the St. Anthony Falls Laboratory at the University of Minnesota. Three-dimensional three-component (3D3C) velocity measurements were made in the flow downstream of the miniature underwater turbine. Wake evolution, turbulence characteristics and primary three-dimensional flow features were identified in the instantaneous and ensemble-averaged flows at different locations downstream of the turbine.