Measuring and modeling the hydraulic effect of hydrokinetic energy extraction in the Tanana River, Alaska

During September of 2014 and July of 2015, a 1.93 m diameter, open-center style, hydrokinetic device was deployed in the Tanana River (Alaska). River velocity was roughly 1.7 m/s and 2 m/s at the deployment site during September 2014 and July 2015 respectively. Using acoustic instruments, velocity and turbulence were measured in the vicinity of the turbine deployment location -- with and without a turbine deployed -- in order to characterize the impact of the turbine on river hydraulics and turbulence (including turbulent kinetic energy, turbulence intensity, and spectra). In addition, river hydraulics -- with and without a turbine deployed -- were modeled using a version of the Environmental Fluid Dynamics Code modified by Sandia National Labs to represent hydrokinetic devices. Measured and modeled velocity in the device's wake (5.2 meters downstream of the device) indicated a 0.38 m/s and a 0.18 m/s reduction in velocity, respectively. The Acoustic Doppler Current Profiler (ADCP) field measurements indicate that velocity is 97.5% recovered at 15.5 turbine diameters, while the model shows 97.5% recovery at 20.2 turbine diameters downstream. Likewise, field Acoustic Doppler Velocimeter (ADV) measurements from a separate testing day showed velocities being 97.5% recovered within 15.5 turbine diameters and fully recovered within 20.7 turbine diameters. ADV measurements indicate a 520% increase in turbulence intensity (TI), which appears to resolve within 20.7 turbine diameters. The effects on the sedimentary environment of a running turbine appear to be minimal. However there is a slight reduction in turbidity in the near field wake of the turbine.