Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session D13: Focus Session: Marine Hydrokinetic Energy Conversion II |
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Chair: Martin Wosnik, University of New Hampshire Room: 301 |
Sunday, November 24, 2013 2:15PM - 2:28PM |
D13.00001: Real-time Ocean Wave Prediction for Optimal Performance of a Wave Energy Converter Daniele Cavaglieri, Thomas Bewley In recent years, there has been a growing interest in renewable energy. Among all the available possibilities, wave energy conversion, due to the huge availability of energy that the ocean could provide, represents nowadays one of the most promising solutions. However, the efficiency of a wave energy converter for ocean wave energy harvesting is still far from making it competitive with more mature fields of renewable energy, such as solar and wind energy. One of the main problems is related to the inability to accurately predict the profile of oncoming waves approaching the wave energy converter. For this reason, we developed a new hybrid method for state estimation of nonlinear systems, which is based on a variational formulation of an ensemble smoother, combined with the formulation of the ensemble Kalman smoother. This method has been employed for the optimal forecasting of ocean waves via sensors placed on an array of wave energy converters. The coupled simulation of ocean waves and energy devices has been carried out leveraging a nonlinear High Order Spectral code. [Preview Abstract] |
Sunday, November 24, 2013 2:28PM - 2:41PM |
D13.00002: Model Scaling of Hydrokinetic Ocean Renewable Energy Systems Karl von Ellenrieder, William Valentine Numerical simulations are performed to validate a non-dimensional dynamic scaling procedure that can be applied to subsurface and deeply moored systems, such as hydrokinetic ocean renewable energy devices. The prototype systems are moored in water 400 m deep and include: subsurface spherical buoys moored in a shear current and excited by waves; an ocean current turbine excited by waves; and a deeply submerged spherical buoy in a shear current excited by strong current fluctuations. The corresponding model systems, which are scaled based on relative water depths of 10 m and 40 m, are also studied. For each case examined, the response of the model system closely matches the scaled response of the corresponding full-sized prototype system. The results suggest that laboratory-scale testing of complete ocean current renewable energy systems moored in a current is possible. [Preview Abstract] |
Sunday, November 24, 2013 2:41PM - 2:54PM |
D13.00003: ABSTRACT WITHDRAWN |
Sunday, November 24, 2013 2:54PM - 3:07PM |
D13.00004: Effect of flow rate and concentration difference on reverse electrodialysis system Kilsugn Kwon, Jaesuk Han, Daejoong Kim Various energy conversion technologies have been developed to reduce dependency on limited fossil fuels, including wind power, solar power, hydropower, ocean power, and geothermal power. Among them, reverse electrodialysis (RED), which is one type of salinity gradient power (SGP), has received much attention due to high reliability and simplicity without moving parts. Here, we experimentally evaluated the RED performance with several parameters like flow rate of concentrated and dilute solution, concentration difference, and temperature. RED was composed of endplates, electrodes, spacers, anion exchange membrane, and cation exchange membrane. Endplates are made by a polypropylene. It included the electrodes, flow field for the electrode rinse solution, and path to supply a concentrated and dilute solution. Titanium coated by iridium and ruthenium was used as the electrode. The electrode rinse solution based on hexacyanoferrate system is used to reduce the power loss generated by conversion process form ionic current to electric current. Maximum power monotonously increases as increasing flow rate and concentration difference. Net power has optimal point because pumping power consumption increases with flow rate. [Preview Abstract] |
Sunday, November 24, 2013 3:07PM - 3:20PM |
D13.00005: Investigation of Energy Harvesting Using Flapping Foils Amin Mivehchi, Amanda Persichetti, Brandon Dunham, Jason M. Dahl When harvesting kinetic energy using a flapping foil, the separation of coherent structures in the wake is crucial for determining forces on the body. Applications for utilizing energy harvesting with a flapping foil include powering of local, low power equipment and recharging AUV batteries that use flapping foils for propulsion and maneuvering. In each of these cases, it is critical to accurately predict the physical behavior and location of vortices in relation to the motion of the body in order to maximize energy output. A two-dimensional open source boundary data immersion method (LilyPad) is used for simulating the flapping motion of a foil for energy harvesting in a current. Forced motion of the flapping body indicates theoretical efficiencies for energy harvesting near 43 percent under specific flapping conditions. A simple control scheme based on pressure sensing on the surface of the foil is developed to control pitch of the foil while energy harvesting occurs in the heave direction. The control scheme is tested through real time numerical simulation. Comparisons are made with physical laboratory experiments, demonstrating high efficiencies in energy harvesting. [Preview Abstract] |
Sunday, November 24, 2013 3:20PM - 3:33PM |
D13.00006: The Impact of Blade Roughness and Biofouling on the Performance of a Horizontal Axis Marine Current Turbine Karen Flack, Jessica Walker, Michael Schultz, Ethan Lust The impact of blade roughness and biofouling on the performance of a two-bladed horizontal axis marine current turbine was investigated experimentally and numerically. A 0.8 m diameter rotor (1/25th scale) with a NACA 63-618 cross section was tested in a towing tank. The torque, thrust and rotational speed were measured in the range 5 \textless $\lambda $ \textless 11 ($\lambda =$ tip speed ratio). Three different cases were tested: clean blades, artificially fouled blades and roughened blades. The performance of the turbine was predicted using Blade Element Momentum theory and validated using the experimental results. The lift and drag curves necessary for the numerical model were obtained by testing a 2D NACA 63-618 airfoil in a wind tunnel under clean and roughened conditions. The numerical model predicts the trends that were observed in the experimental data for roughened blades. The artificially fouled blades did not adversely affect turbine performance, as the vast majority of the fouling sheared off. For the case of roughened blades, the power coefficient (C$_{\mathrm{P}})$ versus $\lambda $ curve was significantly offset below that for the clean case. The maximum C$_{\mathrm{P\thinspace }}$for this condition was 0.34, compared to 0.42 for the clean condition. [Preview Abstract] |
Sunday, November 24, 2013 3:33PM - 3:46PM |
D13.00007: The Influence of depth and surface waves on marine current turbine performance Ethan Lust, Karen Flack, Luksa Luznik, Max Van Benthem, Jessica Walker Performance characteristics are presented for a 1/25$^{\mathrm{th}}$ scale marine current turbine operating in calm conditions and in the presence of intermediate and deep water waves. The two-bladed turbine has radius of 0.4 m and a maximum blade pitch of 17$^{\circ}$. The hydrofoil is a NACA63-618 which was selected to be Reynolds number independent for lift in the operational range (Re$_{\mathrm{C}} =$ 2 - 4 x 10$^{5})$. The experiments were performed in the 116 m tow-tank at the United States Naval Academy at depths of 0.8D and 1.75D measured from the blade tip to the mean free surface. Overall average values for power and thrust coefficient were found to be insensitive to wave form and weakly sensitive to turbine depth. Waves yield a small increase in turbine performance which can be explained by Stokes drift. Variations on performance parameters are on the same order of magnitude as the average value especially near the mean free surface and in the presence of high energy waves. [Preview Abstract] |
Sunday, November 24, 2013 3:46PM - 3:59PM |
D13.00008: Characterizing Turbulent Events at a Tidal Energy Site from Acoustic Doppler Velocity Observations Katherine McCaffrey, Baylor Fox-Kemper, Peter Hamlington As interest in marine renewable energy increases, observations are crucial to understanding the environments encountered by energy conversion devices. Data obtained from an acoustic Doppler current profiler and an acoustic Doppler velocimeter at two locations in the Puget Sound, WA are used to perform a detailed analysis of the turbulent environment that is expected to be present at a turbine placed in a tidal strait. Metrics such as turbulence intensity, structure functions, probability density functions, intermittency, coherent turbulence kinetic energy, anisotropy invariants, and linear combinations of eigenvalues are used to characterize the turbulence. The results indicate that coherent turbulence kinetic energy and turbulence intensity can be used to identify and parameterize different turbulent events in the flow. An analysis of the anisotropy characteristics leads to a physical description of turbulent events (defined using both turbulence intensity and coherent turbulent kinetic energy) as being dominated by one component of the Reynolds stresses. During non-turbulent events, the flow is dominated by two Reynolds stress components. The importance of these results for the development of realistic models of energy conversion devices is outlined. [Preview Abstract] |
Sunday, November 24, 2013 3:59PM - 4:12PM |
D13.00009: Experimental Investigation of Effects of Blockage and Free Surface Proximity on Flow-field and Performance of a Hydrokinetic Turbine Nitin Kolekar, Arindam Banerjee Results from an experimental study to investigate the effect of blockage and free surface proximity on the performance of a constant chord, zero twist, fixed pitch hydro kinetic turbine in an open surface water channel will be presented. The presence of free surface and the size of turbine relative to the flow channel (blockage effect) affects the fluid dynamics around and in the near wake of turbine and hence the thrust-torque loading on turbine blades. Detailed parametric studies will be carried out to understand the effect of free surface proximity, Froude number (which depends on water velocity and depth of the channel), turbine proximity to channel walls and blockage on the turbine performance. Characterization of wake meandering and flow around the turbine is performed using a stereo-Particle Image Velocimetry technique for flows with various Froude number. The thrust and torque on turbine will be measured using a submerged thrust-torque sensor in-line with the turbine. The results of experiments will be compared with analytical models based on blade element momentum theory by modeling free surface and blockage effects. [Preview Abstract] |
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