Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session M2: Industrial Application: Marine Hydrokinetic Turbines |
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Chair: Martin Wosnik, University of New Hampshire Room: A106 |
Tuesday, November 22, 2016 8:00AM - 8:13AM |
M2.00001: Cross-flow turbines: progress report on physical and numerical model studies at large laboratory scale Martin Wosnik, Peter Bachant Cross-flow turbines show potential in marine hydrokinetic (MHK) applications. A research focus is on accurately predicting device performance and wake evolution to improve turbine array layouts for maximizing overall power output, i.e., minimizing wake interference, or taking advantage of constructive wake interaction. Experiments were carried with large laboratory-scale cross-flow turbines $D\sim O(1m)$ using a turbine test bed in a large cross-section tow tank, designed to achieve sufficiently high Reynolds numbers for the results to be Reynolds number independent with respect to turbine performance and wake statistics, such that they can be reliably extrapolated to full scale and used for model validation. Several turbines of varying solidity were employed, including the UNH Reference Vertical Axis Turbine (RVAT) and a 1:6 scale model of the DOE-Sandia Reference Model 2 (RM2) turbine. To improve parameterization in array simulations, an actuator line model (ALM) was developed to provide a computationally feasible method for simulating full turbine arrays inside Navier-Stokes models. Results are presented for the simulation of performance and wake dynamics of cross-flow turbines and compared with experiments and body-fitted mesh, blade-resolving CFD. [Preview Abstract] |
Tuesday, November 22, 2016 8:13AM - 8:26AM |
M2.00002: Advancing marine hydrokinetic turbine arrays towards large-scale deployments in sandy rivers: a laboratory study. Mirko Musa, Craig Hill, Michele Guala A staggered array of twelve axial-flow marine hydrokinetic (MHK) turbine models was investigated at the St. Anthony Falls Laboratory under live-bed sediment transport conditions. In particular, the interaction between the MHK power plant and the complex migrating bedforms was monitored using a state-of-the-art high-resolution submersible laser scanning device able to provide spatio(x,y)-temporally(t) resolved channel bathymetry z(x,y,t). Results revealed both a local signature of each individual turbine and a cumulative array effect that extends farther from the site. Single turbine localized scour results from the blockage effect of the operating rotor and the consequent flow acceleration between the lower rotor tip and the erodible bed. The resultant shear stress enhancement around the device protects the turbine during extreme sediment transport conditions, ultimately preventing the blades from impacting the incoming bedforms. A turbine failure case was simulated to illustrate the consequence of such event, which can irreversibly bury and damage the turbine. Additionally, velocity and turbine performance estimates provided a preliminary description of the power plant energy output, revealing similar features already observed in experimental wind farm models. [Preview Abstract] |
Tuesday, November 22, 2016 8:26AM - 8:39AM |
M2.00003: Field scale simulation of axial hydrokinetic turbines in a natural marine environment Saurabh Chawdhary, Dionysios Angelidis, Lian Shen, Fotis Sotiropoulos Commercialization of marine and hydrokinetic (MHK) energy technologies is still in the development stage. Existing technologies need fundamental research to enable efficient energy extraction from identified MHK sites. We propose a large eddy simulation (LES)-based framework to investigate the site-specific flow dynamics past MHK arrays in a real-life marine environment. To this end, we use advanced computational tools developed at the Saint Anthony Falls Laboratory (SAFL) to resolve the vast range of scales present in the flow. The new generation unstructured Cartesian flow solver, coupled with a sharp interface immersed boundary method for 3D incompressible flows, is used to numerically investigate New York City's East River, where an array of MHK turbines is to be deployed as part of the Roosevelt Island Tidal Energy (RITE) Project. Multi-resolution simulations on locally refined grids are used to simulate the flow in a section of the East River with detailed river bathymetry and inset turbines at field scale. The results are analyzed in terms of the wake recovery, overall wake dynamics, and the power produced by the turbines. These results will help develop design guidelines for the site-specific turbine array configuration. [Preview Abstract] |
Tuesday, November 22, 2016 8:39AM - 8:52AM |
M2.00004: Performance Characteristics of a Vertical Axis Hydrokinetic Turbine Benjamin Bailin, Karen Flack, Ethan Lust Performance characteristics are presented for a vertical axis hydrokinetic turbine designed for use in a riverine environment. The test turbine is a 1:6 scale model of a three-bladed device (9.5 m span, 6.5 m diameter) that has been proposed by the Department of Energy. Experiments are conducted in the large towing tank (116 m long, 7.9 m wide, 5 m deep) at the United States Naval Academy. The large scale facility allows for scale independent results. The turbine is towed beneath a moving carriage at a constant speed in combination with a shaft brake to achieve the desired tip speed ratio (TSR) range. The measured quantities of turbine thrust, torque and RPM result in power and thrust coefficients for a range of TSR. Results will be presented for cases with quiescent flow and flow with mild surface waves, representative of riverine environments. [Preview Abstract] |
Tuesday, November 22, 2016 8:52AM - 9:05AM |
M2.00005: Wake Survey of a Marine Current Turbine Under Steady Conditions Ethan Lust, Luksa Luznik, Karen Flack A submersible particle image velocimetry (PIV) system was used to study the wake of a horizontal axis marine current turbine. The turbine was tested in a large tow tank facility at the United States Naval Academy. The turbine is a 1/25th scale model of the U.S. National Renewable Energy Laboratory's Reference Model 1 (RM1) tidal turbine. It is a two-bladed turbine measuring 0.8 m in diameter and featuring a NACA 63-618 airfoil cross section. Separate wind tunnel testing has shown the foil section used on the turbine to be Reynolds number independent with respect to lift at the experimental parameters of tow carriage speed (U$_{\mathrm{tow}} \quad =$ 1.68 m/s) and tip speed ratio (TSR $=$ 7). The wake survey was conducted over an area extending 0.25D forward of the turbine tip path to 2.0D aft, and to a depth of 1.0D beneath the turbine output shaft in the streamwise plane. Each field of view was approximately 30 cm by 30 cm, and each overlapped the adjacent fields of view by 5 cm. The entire flow field was then reconstructed into a single field of investigation. Results include streamwise and vertical ensemble average velocity fields averaged over approximately 1,000 realizations, as well as higher-order statistics. Turbine tip vortex centers were identified and plotted showing increasing aperiodicity with wake age. keywords: horizontal axis marine current turbine, particle image velocimetry, towing tank, wake survey [Preview Abstract] |
Tuesday, November 22, 2016 9:05AM - 9:18AM |
M2.00006: Influence of surface gravity waves on near wake development behind a towed model horizontal axis marine current turbine Luksa Luznik, Karen Flack, Ethan Lust 2D PIV measurements in the near wake flow field (x/D\textless 2) are presented for a 1/25 scale, 0.8 m diameter (D) two bladed horizontal axis tidal turbine. All measurements were obtained in the USNA 380 ft tow tank with turbine towed at a constant carriage speed (Utow $=$ 1.68 m/s), at the nominal tip speed ratio (TSR) of 7 and incoming regular waves with a period of 2.3 seconds and 0.18 m wave height. Near wake mapping is accomplished by ``tiling'' phase locked individual 2D PIV fields of view (nominally 30x30 cm$^{\mathrm{2}})$ with approximately 5 cm overlap. The discussion will focus on the downstream evolution of coherent tip vortices shed by the rotor blades and their vertical/horizontal displacements by the wave induced fluctuations. This observed phenomena ultimately results in significantly increased downstream wake expansion in comparison with the same conditions without waves. [Preview Abstract] |
Tuesday, November 22, 2016 9:18AM - 9:31AM |
M2.00007: The effect of active control on the performance and wake characteristics of an axial-flow Marine Hydrokinetic turbine Craig Hill, Katherine VanNess, Andy Stewart, Brian Polagye, Alberto Aliseda Turbulence-induced unsteady forcing on turbines extracting power from river, tidal, or ocean currents will affect performance, wake characteristics, and structural integrity. A laboratory-scale axial-flow turbine, $0.45~m$ in diameter, incorporating rotor speed sensing and independent blade pitch control has been designed and tested with the goal of increasing efficiency and/or decreasing structural loading. Laboratory experiments were completed in a 1 m wide, 0.75 m deep open-channel flume at moderate Reynolds number ($Re_c=6~10^4 -– 2~10^5$) and turbulence intensity ($T.I.=2-10\%$). A load cell connecting the hub to the shaft provided instantaneous forces and moments on the device, quantifying turbine performance under unsteady inflow and for different controls. To mitigate loads, blade pitch angles were controlled via individual stepper motors, while a six-axis load cell mounted at the root of one blade measured instantaneous blade forces and moments, providing insights into variable loading due to turbulent inflow and blade-tower interactions. Wake characteristics with active pitch control were compared to fixed blade pitch and rotor speed operation. Results are discussed in the context of optimization of design for axial-flow Marine Hydrokinetic turbines. [Preview Abstract] |
Tuesday, November 22, 2016 9:31AM - 9:44AM |
M2.00008: Experimental Validation of a Theory for a Variable Resonant Frequency Wave Energy Converter (VRFWEC) Minok Park, Louis Virey, Zhongfei Chen, Simo Mäkiharju A point absorber wave energy converter designed to adapt to changes in wave frequency and be highly resilient to harsh conditions, was tested in a wave tank for wave periods from 0.8 s to 2.5 s. The VRFWEC consists of a closed cylindrical floater containing an internal mass moving vertically and connected to the floater through a spring system. The internal mass and equivalent spring constant are adjustable and enable to match the resonance frequency of the device to the exciting wave frequency, hence optimizing the performance. In a full scale device, a Permanent Magnet Linear Generator will convert the relative motion between the internal mass and the floater into electricity. For a PMLG as described in Yeung et al. (OMAE2012), the electromagnetic force proved to cause dominantly linear damping. Thus, for the present preliminary study it was possible to replace the generator with a linear damper. While the full scale device with 2.2 m diameter is expected to generate $O$(50 kW), the prototype could generate $O$(1 W). For the initial experiments the prototype was restricted to heave motion and data compared to predictions from a newly developed theoretical model (Chen, 2016). [Preview Abstract] |
Tuesday, November 22, 2016 9:44AM - 9:57AM |
M2.00009: Results from the field test of two 1 kW oscillating hydrofoil generators in a tidal canal Michael Miller, Jennifer Cardona, Leanne Block, Kenta Kondo, Michael Lee, Rebecca Lorick, Michael Manning, Isabel Scherl, Filip Simeski, Arriane Spaulding, Yunxing Su, David Ellerby, Erika Sudderth, Kristen Lewis, James Kidd, William Hubbard, Hung Tom Pham, Tom Derecktor, Steve Winckler, Alice Fawzi, Jennifer Franck, Kenneth Breuer, Shreyas Mandre We present results from field tests of two 1 kW hydrokinetic energy capture devices operating in the Cape Cod Canal, in Bourne, MA. Each device consists of two oscillating hydrofoils with a chord of 0.24 m and span of 1.35 m, operating 90$^\circ$ out of phase with each other and driving a single generator. The pitch of each hydrofoil is mechanically coupled to the heave, also with a 90$^\circ$ phase difference. The two devices are arranged in tandem with a stream-wise separation of 1 span. We find that depending on the operating conditions, the hydrofoil oscillations may synchronize with each other through hydrodynamic interactions. Furthermore, in their optimized operation, the trailing device generates 60-80% of the power generated by the leading device, despite being directly in the wake of the hydrofoils of the upstream device. [Preview Abstract] |
Tuesday, November 22, 2016 9:57AM - 10:10AM |
M2.00010: Wingtip Devices for Marine Applications Ivaylo Nedyalkov, Timothy Barrett, Aleksandra Wojtowicz, Martin Wosnik Wingtip devices are widely used in aeronautics, and have been gaining popularity in wind and marine turbine applications. Although the principles of operation of the devices in air and water are similar, one major difference in the marine environment is the presence of cavitation. In an integrated numerical and experimental study, three wingtip devices were attached to an elliptical foil and compared to a reference case (no wingtip). Lift, drag, and cavitation characteristics were obtained both numerically (in OpenFOAM) and experimentally (in the University of New Hampshire High-Speed Cavitation Tunnel). As expected, with the addition of wingtip devices, the maximum lift/drag ratio increases and tip vortex cavitation is suppressed. The next step in the study is to develop a theoretical relationship between tip-vortex cavitation inception and flow parameters for foils with non-elliptical load distribution, such as foils with wingtips. [Preview Abstract] |
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