Marine hydrokinetic (MHK) energy conversion, comprised of tidal/ocean current and wave energy, is likely one of the more environmentally sustainable ways to generate electricity. The overall objective of this project is to better understand the spatio-temporal structure of the turbulent inflow and wakes at scales relevant to marine hydrokinetic energy conversion. A suite of state-of-the-art experimental fluid dynamics instrumentation will be employed for turbulence characterization, and both laboratory and open water (tidal estuary) test facilities will be used. The study will focus on tidal energy, however, the results are applicable to ocean and river current energy conversion and wave energy as well.
Intellectual Merit: MHK energy conversion devices are subjected to a wide range of turbulent scales. For example, the fastest tidal currents often occur in regions of complex bathymetry, which creates complex boundary layers and flow distortions in locations where MHK devices will be sited. Initial tests have shown that the performance of MHK devices, as well as structural fatigue and failure, are closely linked to turbulence. Downstream, turbulence generated by MHK devices and their support structures can have an effect on the environment and organisms in the water column. The robust Acoustic Doppler Current Profilers (ADCPs) commonly used for open water measurements are limited to low sampling rates due to their operational principle, which results in insufficient spatial resolution for scales of turbulence relevant to MHK devices. On the other hand, experimental techniques with higher temporal and spatial resolution are typically limited to laboratory environments. For this project, turbulent inflow and hydrokinetic turbine wakes will first be measured in a large cross-section combined tow-wave tank comparing ADCPs, multi-point Acoustic Doppler Velocimetry (ADV) and underwater high frame-rate Particle Image Velocimetry (HFR-PIV), to establish baselines on how each instrument measures spatio-temporal flow structures. Then turbulent inflow and hydrokinetic turbine wakes will be measured at an open-water tidal energy test site comparing ADCP and ADV. Data from the laboratory and the open-water deployments will be used in mathematical modeling with low-dimensional model and stochastic estimation techniques to predict turbulent flow states from ADCP profiles and ADV reference measurements. The project will thus fill an instrumentation ?scale gap? that currently exists.
Broader Impacts: The project will produce previously unavailable information on the spatio-temporal structure of MHK-relevant flows. It will improve our understanding of the capabilities of the different measurement techniques in an MHK environment and create general predictive tools, which will make possible the study of other phenomena and processes in the marine environment. The results of this research will enable higher-fidelity resource assessment and more accurate energy conversion device evaluation, yield previously inaccessible flow data for fluid-structure interaction, generate data for device array layouts, facilitate environmental impact assessments, and, ultimately, lead to improved designs. It will thus help the United States? MHK industry to become successful. The integration of research and education activities will be achieved through inclusion of research in senior/graduate courses in Renewable Energy and Experimental Fluid Dynamics, industrial research opportunities as part of graduate training, outreach and continuing education, and participation in university open house events, laboratory tours and demonstrations. The outreach will include activities with the NH Seacoast Science Center and the NH Children?s Museum. Underrepresented groups in engineering will be actively recruited through the UNH Office of Diversity and student societies, to work on the proposed research as undergraduate researchers and potential Ph.D. students. The project will be used to attract students interested in the fields of renewable energy, flow measurement and turbulence, and help train the workforce necessary for advancing this new industry.
