| NSF Org: |
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems |
| Recipient: |
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| Initial Amendment Date: | January 28, 2012 |
| Latest Amendment Date: | January 28, 2012 |
| Award Number: | 1150797 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Carole Read
cread@nsf.gov (703)292-2418 CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems ENG Directorate for Engineering |
| Start Date: | February 1, 2012 |
| End Date: | September 30, 2018 (Estimated) |
| Total Intended Award Amount: | $401,456.00 |
| Total Awarded Amount to Date: | $401,456.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
51 COLLEGE RD DURHAM NH US 03824-2620 (603)862-2172 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
24 Colovos Rd Durham NH US 03824-3515 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | EchemS-Electrochemical Systems |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
1150797-Wosnik
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.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Marine and hydrokinetic (MHK) energy conversion, which includes tidal/ocean current and wave energy, is viewed as an environmentally sustainable way to generate electricity. The project studied turbulent flows relevant to MHK energy conversion, such as turbulent inflow and turbine wake development. A certain type of MHK turbines, so-called cross-flow turbines, were studied in more detail, with a purpose-built high-resolution test bed in a large cross-section towing tank and with numerical modeling. Open water experiments were conducted in a tidal estuary with turbines deployed from a floating platform.
Intellectual merit:
The overall objective of this project was to better understand the spatio-temporal structure of turbulent inflow and wakes at scales relevant to marine hydrokinetic energy conversion, obtain turbine performance data and flow measurements using state-of-the-art experimental fluid dynamics instrumentation, and create public databases for model validation and verification.
It was demonstrated that experiments with cross-flow MHK turbines need to be conducted above a certain threshold combination of turbine size and flow velocity (Reynolds number) so that results can be extrapolated to full scale in a meaningful way, e.g., when using experimental data to validate numerical simulations. Guidelines for experiments with this type of turbine were established.
Detailed performance and near-wake measurements with two reference turbines identified the physical mechanism driving the rapid wake recovery of cross-flow turbines, and provided evidence why certain numerical models (e.g., vortex models) will not be able to accurately capture the flow physics of cross-flow turbines.
An actuator-line model for cross flow turbines, which treats turbine blades as lines of actuator elements, was developed in the open-source computational fluid dynamics (CFD) environment OpenFOAM. This model is a combination of classical blade element theory and Navier-Stokes based numerical models, and bridges the gap between high and low fidelity numerical modeling tools for cross-flow turbines.
It was demonstrated that acoustic Doppler current profiler (ADCP) measurements with low spatial and temporal resolution – which are under-resolved to accurately measure turbulence – can be corrected with a mathematical model to correspond to the turbulence measurements from an acoustic Doppler velocimeter (ADV) with much higher spatial and temporal resolution.
First measurements of turbulent inflow and wake of an MHK turbine deployed at an open-water tidal test site were obtained.
Broader Impacts:
Previously unavailable data on spatio-temporal structure of marine hydrokinetic energy conversion-relevant flows were generated. This type of data is needed to validate numerical models for turbine performance and higher level array or environmental transport models. The results from this project will enable more accurate energy conversion device evaluation, inform device array layouts and facilitate environmental impact and techno-economic risk assessments for the nascent marine hydrokinetic energy conversion industry.
Several databases for model validation and verification were published: (1) UNH reference vertical axis turbine: baseline performance and near-wake measurements, (2) UNH reference vertical axis turbine: Reynolds number dependence experiment, (3) UNH/Sandia experiments with DOE-Sandia reference model 2 (RM2), (4) Case files for Actuator Line Model (ALM) for cross-flow turbines, written as an extension library in OpenFOAM. The databases include the processing code used to obtain results presented in journal papers. All databases are public, hosted on figshare.com and have Digital Object Identifiers (DOI).
Other projects were enabled by the hardware and software developed under this NSF CAREER grant. For example, the first successful in-water fiber-Bragg grating (FBG) optical strain measurements on turbine blades of a working marine hydrokinetic turbine were conducted using the turbine test bed developed under this grant.
The project trained one Ph.D. student, and contributed to the training of one other Ph.D. student and five M.S. students. Undergraduate students were involved in the project through several 9-month long capstone senior projects and outreach activities.
A highlight among the many outreach activities was the annual UNH Ocean Discovery Day, which reaches a large number of participants from groups underrepresented in STEM. Outreach included hardware exhibits, tow tank demonstrations, movies and presentations related to this project.
Results and insights from this project were incorporated in marine renewable energy modules in a new senior level technical elective/graduate course, “ME 706/806 Physical and Engineering Principles of Renewable Energy Conversion”. After ramp-up, this course regularly enrolled more than 50 senior and graduate engineering students each year.
Results were disseminated through theses at the University of New Hampshire, archival publications in peer-reviewed journals, conference presentations and proceedings, and invited seminars and presentations.
Last Modified: 04/12/2019
Modified by: Martin M Wosnik
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