Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session A06: Energy Harvesting and Power Generation I |
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Chair: Oscar Curet, Florida Atlantic University Room: Georgia World Congress Center B208 |
Sunday, November 18, 2018 8:00AM - 8:13AM |
A06.00001: Mangrove-Like System for Harvesting Tidal Energy Daniel O. Gómez, Eduardo E. Castillo, Amirkhosro Kazemi, Oscar M Curet A mangrove-like system to harvest hydrokinetic energy from tidal stream was designed and tested for different flow conditions. The energy harvesting system was composed of an array of cylinders hinged at a pivot point above the water’s surface allowing one degree of freedom. An electric generator composed of a pair of magnets attached of the cylinders and a winding was used to transfer the mechanical motion to electrical energy. The model was tested in a water for different patch configurations, hinged stiffness’s and flow velocities ranging from 2 to 15 cm/s. The patch kinematics and voltage with no load were measured. In addition, the wake downstream the patch was measured with particle image velocimetry. It was found that the patch started to oscillate after reaching some critical velocity. As the spacing between the cylinders increased the critical velocity to start the oscillation decreased. We present the hydrodynamics and performance of the energy harvesting system for the different conditions considered. Our results suggest that the cylinder arrangement and hinged stiffness can be tuned arrays to maximize the energy harvested at different flow conditions. |
Sunday, November 18, 2018 8:13AM - 8:26AM |
A06.00002: Oscillations of a Modeled Mangrove-Root for Energy Harvesting and Hydrodynamics Characterization Eduardo Enrique Castillo, Daniel O. Vazquez, Amirkhosro Kazemi, Oscar M Curet A one-degree-of-freedom vortex induced vibration (VIV) was investigated to measure the energy extracted from oscillations of the mangrove roots. A mangrove root was modeled as a vertical cylinder (Cyl), submerged in a water tunnel, pivoted at its top by a thin steel plate. This enhance transverse oscillations, perpendicular to the water flow. Three plates thickness were used to simulate diverse root’s rigidity. A generator was attached to the Cyl and the voltage was measured. The oscillation amplitude (OA) of the Cyl tip was recorded with HS camera and 2-D PIV measurements were made. The Cyl was still for low water velocities, then OA increase very fast reaching a maximum, and decrease until a very low value. Contrary, frequency of the OA was always increasing with water velocity. Similar behavior was found for all rigidities, but the critical values also increase with rigidity. The rms voltage follows similar tendency than OA with a maximum of 28 mV for the case of maximum rigidity. The analysis of downstream vortex shedding data extracted from PIV will be used to correlate with mechanical energy conversion of the root and with the electrical energy. This analysis of VIV correlated with oscillations will be fundamental for future bio-inspired energy harvesting devices. |
Sunday, November 18, 2018 8:26AM - 8:39AM |
A06.00003: On enhancing the energy capture in a downstream rotor tidal energy converter by using pylon fairings Arindam Banerjee, Ashwin Vinod, Jonathan Colby Tidal energy converters where the flow encounters an upstream pylon prior to the rotor are known to create a velocity deficit at the rotor plane, affecting its power capture. In addition, the pylon wake escalates load fluctuations on the rotor, increasing the fatigue loading on the blades. The ongoing collaboration between Lehigh University and Verdant Power, Inc. aims to explore the effects of various fairing shapes on the pylon wake characteristics. Pylons tested employed downstream fairings composed of straight, convex, and concave plates. A pylon with fairings both upstream and downstream, referred to as the Double Fairing was also developed. All designs were tested at Re = 2×104, two levels of elevated turbulence mimicking tidal energy sites (6% and 18%, generated using an active grid) and two yaw states; 0o and 15°. Of all tested fairings, the double fairing appeared to be the most effective, with a yawed double fairing further improving power capture by 2.25%. Elevated turbulence was found to increase power capture by 1%. Tests at Re = 6×104 are underway to better stimulate boundary layer transition and will also be presented at the conference. |
Sunday, November 18, 2018 8:39AM - 8:52AM |
A06.00004: Hydrokinetic energy harvesting in large natural rivers: a multifaceted experimental study. Mirko Musa, Michele Guala, Craig Hill, Fotis Sotiropoulos Rivers are currently an overlooked potential source of local and continuous kinetic energy that can be harnessed using the present in-stream converters technology. An experimental study was carried out in a quasi-field-scale channel at the Saint Anthony Falls Laboratory to investigate the feasibility of hydrokinetic turbine power plant deployments in large morphodynamically active rivers. A staggered array of twelve axial-flow hydrokinetic turbine models was deployed on one side of the channel, under intense sediment transport conditions. The 2D bathymetry evolution was monitored using a high-resolution submersible laser scanning device, revealing both the local erosion at the base of each individual turbine and a cumulative array-scale effect on the averaged topography. The enhanced shear stress resulting from the operating turbine and responsible for the local scour, is also interpreted as a self-defense mechanism which prevents the large approaching dunes from encroaching on the blades. Turbines wake and performance were characterized through the array, revealing similar features already observed in experimental wind farm models. Results indicate that the staggered configuration is beneficial for both wake recovery and power output. |
Sunday, November 18, 2018 8:52AM - 9:05AM |
A06.00005: Evaluation of different dynamic mesh techniques with direct application to computational fluid dynamic analysis of a marine hydrokinetic cross-flow turbine Minh Nhat Doan, Ivan Alayeto, Kana Kumazawa, Shinnosuke Obi We present 4 different dynamic mesh techniques that could be applied directly to solve for the incompressible flow around a marine hydrokinetic (MHK) cross-flow turbine. All computational fluid dynamic (CFD) cases model a physical small turbine experiment with rotating mesh, deformable mesh, overset mesh, and moving immersed boundary. The experiment is conducted in a water tunnel facility at the turbine diameter based Reynolds number of 20,000. The near wake velocity field behind a vertical-axis straight three-bladed turbine (0.034 m diameter and 0.025 m chord length) is measured by 2D particle image velocimetry (mono PIV) and compared with results from the CFD analysis. All cases share similar a meshing topology and are solved with OpenFOAM PISO-Simple algorithm. The 4 techniques are assessed based on their accuracy, computational time, and total workload including mesh generation and post-processing. All of the cases can potentially be slightly modified for higher Reynolds number flow or applied to an axial-flow MHK turbine. |
Sunday, November 18, 2018 9:05AM - 9:18AM |
A06.00006: The Effect of Wave Parameters on the Performance of an Axial-Flow Hydrokinetic Turbine Ethan Lust, Peter Hodapp The installation of axial-flow marine hydrokinetic turbines has been proposed for a variety of geographic locations, each with its own unique bathymetry, navigation requirements, environmental considerations, etc. One of the environmental factors that should be taken into consideration is the impact of waves. Surface waves impose an unsteady velocity that can significantly impact turbine power quality and structural loading. In order to further understanding of the impact of surface waves on turbine performance, a series of tests were performed in the small towing-tank facility at the U.S. Naval Academy. The turbine used in the present experiment was a 1:44 scale turbine measuring 0.45 m in diameter and featuring a NACA 4415 airfoil cross-section. Three testing phases, each focusing on a different wave parameter, were run. It was shown that increasing wave height or wavelength, while holding all other parameters constant increased the range of the resulting power coefficient. However, when wave energy per unit width was held constant, even while changing the other parameters, the resulting range of power coefficient values was nearly constant. This suggests that the energy of the wave, not the other parameters, has the most impact on turbine performance. |
Sunday, November 18, 2018 9:18AM - 9:31AM |
A06.00007: Abstract Withdrawn
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Sunday, November 18, 2018 9:31AM - 9:44AM |
A06.00008: RANS Simulations of Oscillating Foils for High-Thrust Marine Propulsion Mukul Dave, Arianne Spaulding, Jennifer A Franck Flow simulations were performed at a high Reynolds number (106) for oscillating foil propulsion over a sweep of pitch, heave and frequency kinematics. The goals are to investigate thrust and efficiency values over the parameter range for bio-inspired propulsion on larger surface vessels such as tug boats and other watercraft. An incompressible RANS solver was used on a two-dimensional domain with dynamic meshing. Results show high efficiencies up to 80% for low frequencies and angles of attack, whereas high thrust coefficient values were obtained at higher frequencies. Further calculations indicated performance comparable to conventional propellers, but with an ability to adapt the kinematics to meet vessel demands in different operational regimes. Contour plots of efficiency and thrust coefficient in terms of Strouhal number and max relative angle of attack provide an insight into modulating the kinematics of the heaving-pitching motion from a high-thrust regime to a high-efficiency regime. Lastly, flow around the hydrofoil and in the wake is classified into different regimes based on nature of flow separation and formation of vortices, demonstrating the effect of hydrodynamics on performance. |
Sunday, November 18, 2018 9:44AM - 9:57AM |
A06.00009: Using cyber-physical pitch-heave systems for both energy harvesting and propulsion Yunxing Su, Kenneth Breuer We report on the use of a cyber-physical system to characterize and optimize the performance of both energy harvesting and propulsion modes using a pitch-heave hydrofoil in uniform flows. Expanding on previous work (e.g. Hover et al. 1997, Mackowski and Williamson 2011), a force-feedback cyber-physical system is used to achieve an elastically-mounted hydrofoil in which active kinematics and/or passive (mass-spring-damper) responses can be achieved in both heave and pitch. A wide range of parameters can be easily explored for use in both energy harvesting or propulsion applications. The system with a prescribed pitch motion and a passive heave motion is appropriate for energy harvesting and we identify the relationship between the forced pitch kinematics and the natural heave dynamics. The effects of non-sinusoidal pitch dynamics, and nonlinear spring stiffness are reported. Propulsion is achieved using active heave with a passive pitch response and the effects of non-sinusoidal kinematics and nonlinear structural dynamics for locomotion are also reported. |
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