"Hydrokinetic energy harvesting based on vortex induced vibration (VIV) of a bluff body is discussed. VIV is defined as the vibration incurred on a bluff body due to an external fluid flowing over it. These vibrations are the results of boundary layer separation from the surface of the body. An optimized VIV generator has been developed, that utilizes a non-contact type linear magnetic device for generation of energy. The cylinder was chosen such that at the mass ratio (m*) was always lower than the critical mass (m*critical= 0.52). The studies were based on two complementary techniques: (a) computational fluid dynamics study to derive the initial design guidelines of our laboratory prototype; and, (b) experimental study to identify optimized design parameters that would allow such a device to maximize the net energy production.
A detailed two-dimensional CFD study was performed at laminar and turbulent flow regimes (45 < Re < 3.2x104). A k-ω Shear Stress Transport turbulence model was chosen in the present study. The results obtained from the laminar flow (Re < 200) suggest a maximum attainable amplitude of ~0.6D.The maximum amplitude was found to be a constant even for the case where the overall mass damping of the system was reduced to zero. Also as seen in experiments, the present numerical study depicted an absence of the upper branch at low values of Reynolds number. For the turbulent flow case (1x104 < Re < 3.2x104), our numerical simulations accurately predicts the appearance of the 2S mode in the initial branch followed by a 2P mode in the upper and lower branches. However, at higher Re, the flow is expected to become three-dimensional (as observed in experiments) and our two-dimensional simulations were unable to predict the amplitudes in the upper branch that were obtained from experiments done in-house. The effect of mass ratio on VIV was studied experimentally for seven different cylinders with varying diameters having mass ratios (m*) from 10.75 to 0.47. Regimes of operation that would maximize the energy harvested from our VIV based generated are identified. Finally, a power take-off system (PTO) based on a Tubular Linear Interior Permanent Magnet (TL-IPM) is proposed and various preliminary design parameters for such a system is discussed"--Abstract, page iii.
Kimball, Jonathan W.
Mechanical and Aerospace Engineering
M.S. in Mechanical Engineering
Missouri University of Science and Technology
xii, 118 pages
© 2012 Varun Michael Lobo, All rights reserved.
Thesis - Open Access
Hydraulic turbines -- Design
Turbulence -- Mathematical models
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Link to Catalog Record
Lobo, Varun Michael, "Design of a vortex induced vibration based marine hydro-kinetic energy system" (2012). Masters Theses. 7443.