Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session E27: Renewable Energy |
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Chair: Mehdi Raessi, University of Massachusetts, Dartmouth Room: 31C |
Sunday, November 18, 2012 4:45PM - 4:58PM |
E27.00001: Energy harvesting of fluttering piezoelectric flags Olivier Doare, Sebastien Michelin, Jiawan Chen, Yifan Xia The energy harvesting from a flutter instability of a plate equipped with adjacent pairs of piezoelectric elements shunted with independent resistive circuits is considered. When the length of the piezoelectric elements is low compared to the typical wavelengths of bending deformations, governing equations are derived in the form of continuous coupled fluid-solid-electrical equations. These equations are used to perform a linear stability analysis of the coupled system, and a parametric study of the efficiency of the energy transfer from the fluid-solid system to the electrical system addressing both linear and nonlinear dynamics. [Preview Abstract] |
Sunday, November 18, 2012 4:58PM - 5:11PM |
E27.00002: Flexible Beams in Turbulent Boundary Layers for Piezoelectric Energy Harvesting Huseyin Dogus Akaydin, Niell Elvin, Yiannis Andreopoulos Thin flexible cantilever beams with patches of piezoelectric materials or surrogates with strain gages attached have been placed inside turbulent boundary layers to search for the maximum energy output. A turbulent boundary layer (TBL) carries mechanical energy distributed over a range of temporal and spatial scales and their interaction with the immersed piezoelectric beams results in a strain field which generates the electrical charge. This energy harvesting method can be used for developing self-powered flow sensors. In the present experimental work TBLs with Re$_{\theta }$ between 1500 and 7700 were configured in a large scale wind tunnel. The orientation of the beam relative to the incoming flow and its distance to the wall was found to be critical parameters affecting the energy output. ``Power maps'' generated by testing a beam in TBLs at different free stream velocities and wall distances will be presented. Vibration amplitudes and frequencies at several principal orientations will be compared. The effect of yaw angle, pitch angle, length and natural frequency of the beam will be examined. The role of instantaneous pressure fluctuations and large-scale TBL structures in this rather complex fluid-structure interaction will be discussed in interpreting the electrical output results. [Preview Abstract] |
Sunday, November 18, 2012 5:11PM - 5:24PM |
E27.00003: On the effects of energetic coherent motions on power and wake dynamics of an axial-flow marine turbine in an open channel Craig Hill, Leonardo Chamorro, Vincent Neary, Budi Gunawan, Roger Arndt, Fotis Sotiropoulos Laboratory experiments are carried out to study the effect of energetic coherent motions on the performance of a model axial-flow hydrokinetic turbine in the main channel at Saint Anthony Falls Laboratory. A mechanical system allows the turbine angular velocity to be precisely specified and maintained via a controller. Power fluctuations are tracked using a torque sensor connected to the turbine structure. Periodic energetic coherent motions are introduced in the flow by placing a cylinder at various locations upstream of the turbine on the plane of symmetry. Three acoustic Doppler velocimeters and a torque sensor are used to obtain synchronous high resolution measurements of the flow and turbine power at a rate of 200 Hz, respectively. Flow measurements are obtained at various locations upstream and downstream of the turbine. The measurements provide novel insights into the role of strong energetic coherent motions on turbine power fluctuations, tip vortex instability, and mean wake recovery. The implications of these findings for the efficient operation of hydrokinetic turbines in natural waterways will be discussed. [Preview Abstract] |
Sunday, November 18, 2012 5:24PM - 5:37PM |
E27.00004: Computational simulation of ocean wave energy converters using the fast fictitious domain method Amirmahdi Ghasemi, Ashish Pathak, Mehdi Raessi Ocean wave energy is considered one of the major renewable energy resources. We are developing a computational tool for analysis of wave energy converters. This computational tool is envisioned to complement and leverage experimental knowledge base, which is expensive or difficult to develop in this field. The computational tool simulates the interaction of two-phase fluid flows with a moving solid object by solving the full Navier-Stokes equations. Unlike previous models, it considers all non-linear effects, e.g. wave breaking and fluid-solid interactions. We use the two-step projection method in the finite-volume context with GPU acceleration to solve the flow equations. The fluid interfaces are tracked by using the volume-of-fluid (VOF) method. We incorporated the fast fictitious-domain method into our flow solver to simulate the interactions of a moving solid object with two-phase flows. Extending Youngs' piecewise linear interface reconstruction technique, we use a geometrical reconstruction of liquid-gas-solid interfaces at the triple point to accurately track the three phases. We will present results of canonical test cases, which demonstrate the accuracy of the above approach, as well as a 2D simulation of a buoy interacting with water waves in a tank. [Preview Abstract] |
Sunday, November 18, 2012 5:37PM - 5:50PM |
E27.00005: An experimental study of small-scale flexible wind turbine blades Pariya Pourazarm, Yahya Modarres-sadeghi, Matthew Lackner With the increasing size of offshore wind turbine rotors, the design criteria used for the blades may also evolve. Current offshore technology utilizes three relatively stiff blades in an upwind configuration. With the goal of minimizing mass, there is an interest in lightweight rotors that instead utilize two flexible blades oriented downwind. These design possibilities necessitate a better understating of the fundamental behavior of such flexible blades. In the current work, a series of experiments are conducted using a small scale wind turbine built with~adjustable features. The blades are designed using relatively thin, low Reynolds number airfoils and built using rapid-prototyping methods with a flexible material. The number of blades as well as their pitch angle, stiffness, and distance from the tower can be varied. The tests are conducted in a wind tunnel with a cross-section of 1 m by 1 m, a wind speed range of 3 to 20 m/s and a turbulence intensity of less than 1{\%}. The small scale wind turbine is tested both upwind and downwind and a dynamic strain gauge is placed on the blades to measure blade deflection and dynamic loading in various configurations. [Preview Abstract] |
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