Development of measurement methods for testing of hydrokinetic devices to evaluate the environmental effect on local substrate

摘要

Modifications and upgrades to the open channel hydraulic flume in the Environmental Fluid Mechanics and Hydraulics Laboratory (EFM&HL) at Bucknell University are described. These changes enable small-scale testing for model marine hydrokinetic (MHK) devices. The flume has dimensions 9.75 m long, 1.22 m wide, and 0.38 m deep. To fully assess the environmental impact of deploying MHK devices in rivers and tidal estuaries, full-scale field testing must be performed. Small-scale studies are a more cost-effective means to predict possible environmental effects on a larger scale. This testing platform is instrumental in yielding physical measurements of how MHK devices affect substrate topology. A nozzle sediment insert has been designed to hold sediment of desired size and material to allow for multiple environments to be tested, as well as increase the flow speed for testing. Acoustic Doppler Velocimetry (ADV) and Color Particle Shadow Velocimetry (CPSV) are used to characterize flow in the test section of the nozzle sediment insert, both span-wise and boundary layer velocity profiles. The span-wise velocity shows that the flow within the test section is both two dimensional and doubles in magnitude when using the nozzle. The boundary layer properties found in the test section are: a thickness of 40 mm, a displacement thickness of 5.16 mm, a momentum thickness of 3.75 m, and a friction velocity of 0.0169 m/s. The facility is also equipped with a 2D sediment bed profiler consisting of both a low-powered laser probe and a touch sensitive probe that accurately measures the topology of the sediment bed. The bed form topology for a 1.27 cm diameter cylinder was validated for the 2D bed profiler with manual point gauge measurements.