Validating and Applying Numerical Models for Current Energy Capture Devices

Abstract:

With the growing focus on renewable energy, there is increased interest in modeling and optimizing current energy capture (CEC) devices. The interaction of multiple wakes from CEC devices can affect optimal placement strategy, and issues of environmental impacts on sediment transport and large-scale flow should be examined. Numerical models of four flume-scale experiments were built using Sandia National Laboratories’ Environmental Fluid Dynamics Code (SNL-EFDC.) Model predictions were calibrated against measured velocities to estimate flow and turbine parameters. The velocity deficit was most sensitive to α_md, the dimensionless Smagorinsky constant related to horizontal momentum diffusion, and to C_PB, the dimensionless partial blockage coefficient accounting for the physical displacement of fluid due to turbine blockage. Calibration to four data sets showed α_md ranged from 0.3 to 1.0 while C_PB ranged from 40 to 300. Furthermore, results of parameter estimation indicated centerline velocity data were insufficient to uniquely identify the turbulence, flow, and device parameters; cross-channel velocity measurements at multiple locations downstream yielded important calibration information and it is likely that vertical velocity profiles would also be useful to the calibration effort. In addition to flume scale models, a full-scale implementation of a CEC device at Roza Canal in Yakima, WA was developed. The model was analyzed to find an appropriate grid size and to understand the sensitivity of downstream velocity profiles to horizontal momentum diffusion and partial blockage coefficients. Preliminary results generally showed that as C_PB increased the wake was enhanced vertically.