Synergistic Flow-Induced Oscillation of Multiple Cylinders in Harvesting Marine Hydrokinetic Energy

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Mengyu Li ◽  
Christopher C. Bernitsas ◽  
Jing Guo ◽  
Hai Sun
Keyword(s):  
Negative Impact ◽  
Flow Speed ◽  
Shielding Effect ◽  
University Of Michigan ◽  
Hydrokinetic Energy ◽  
Close Proximity ◽  
Marine Hydrokinetic ◽  
The University ◽  
Energy Harnessing

Abstract Flow-induced oscillations/vibrations (FIO/V) of cylinders in tandem can be enhanced by proper in-flow spacing to increase hydrokinetic energy harnessing. In a farm of multiple cylinders in tandem, the effect of interference on harnessing efficiency arises. Three years of systematic experiments in the Marine Renewable Laboratory (MRELab) of the University of Michigan, on an isolated cylinder, and two and three cylinders in tandem have revealed that synergistic FIO can enhance oscillations of cylinders in close proximity. Two cylinders in tandem can harness 2.5–13.5 times the hydrokinetic power of one isolated cylinder. Three cylinders in tandem can harness 3.4–26.4 times the hydrokinetic power of one isolated cylinder. Negative impact on the harnessed energy by multiple cylinders, such as the shielding effect for the downstream cylinder/s, is possible. Specifically for the three-cylinder configuration, at a certain flow speed, the decrease in the power of the middle cylinder can be overcome by adjusting its stiffness and/or damping.

Synergistic Flow Induced Oscillation of Multiple Cylinders in Harvesting Marine Hydrokinetic Energy

2019 ◽  
Author(s):  
Sun Hai ◽  
Michael M. Bernitsas ◽  
Chen Zhiyun
Keyword(s):  
University Of Michigan ◽  
Hydrokinetic Energy ◽  
Close Proximity ◽  
Marine Hydrokinetic ◽  
The University ◽  
Energy Harnessing

Abstract Flow Induced Oscillations (FIO) of cylinders in tandem can be enhanced by proper spacing to increase hydrokinetic energy harnessing. In a farm of multiple cylinders in tandem, the issue of the effect of interference on harnessing efficiency arises. Over the course of three years of development in the Marine Renewable Laboratory of the University of Michigan, systematic experiments on an isolated cylinder, and two and three cylinders in tandem have revealed that synergistic FIO can actually enhance oscillations of cylinders in close proximity. Two cylinders in tandem can harness 2.5–13.5 times the hydrokinetic power of one isolated cylinder. Three cylinders in tandem can harness 3.4–26.4 times the hydrokinetic power of one isolated cylinder.

Effect of Bottom Boundary on VIV for Energy Harnessing at 8×103

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
K. Raghavan ◽  
Michael M. Bernitsas ◽  
D. E. Maroulis
Keyword(s):  
Strong Dependence ◽  
Clean Energy ◽  
Reynolds Numbers ◽  
Strong Impact ◽  
University Of Michigan ◽  
Vortex Induced Vibration ◽  
Bottom Boundary ◽  
The University ◽  
Energy Harnessing ◽  
First Time

The concept of extracting energy from ocean/river currents using vortex induced vibration was introduced at the OMAE2006 Conference. The vortex induced vibration aquatic clean energy (VIVACE) converter, implementing this concept, was designed and model tested; VIV amplitudes of two diameters were achieved for Reynolds numbers around 105 even for currents as slow as 1.6 kn. To harness energy using VIV, high damping was added. VIV amplitude of 1.3 diameters was maintained while extracting energy at a rate of PVIVACE=0.22×0.5×pU3DL at 1.6 kn. Strong dependence of VIV on Reynolds number was proven for the first time due to the range of Reynolds numbers achieved at the Low-Turbulence Free Surface Water (LTFSW) Channel of the University of Michigan. In this paper, proximity of VIVACE cylinders in VIV to a bottom boundary is studied in consideration of its impact on VIV, potential loss of harnessable energy, and effect on soft sediments. VIV tests are performed in the LTFSW Channel spanning the following ranges of parameters: Re∊[8×103–1.5×105], m∗∊[1.0–3.14], U∊[0.35–1.15 m/s], L/D∊[6–36], closest distance to bottom boundary (G/D)∊[4−0.1], and m∗ζ∊[0.14–0.26]. Test results show strong impact for gap to diameter ratio of G/D<3 on VIV, amplitude of VIV, range of synchronization, onset of synchronization, frequency of oscillation, hysteresis at the onset of synchronization, and hysteresis at the end of synchronization.

scholarly journals Virtual Spring–Damping System for Flow-Induced Motion Experiments

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Hai Sun ◽  
Eun Soo Kim ◽  
Marinos P. Bernitsas ◽  
Michael M. Bernitsas
Keyword(s):  
First Generation ◽  
Closed Loop ◽  
Hydrodynamic Force ◽  
Circular Cross Section ◽  
Data Generation ◽  
University Of Michigan ◽  
Hydrokinetic Energy ◽  
Vortex Induced Vibrations ◽  
Induced Motion ◽  
The University

Flow-induced motion (FIM) experiments of a single circular cylinder or multiple cylinders in an array involve several configuration and hydrodynamic parameters, such as diameter, mass, damping, stiffness, spacing, Reynolds number, and flow regime, and deviation from circular cross section. Due to the importance of the FIM both in suppression for structural robustness and in enhancement for hydrokinetic energy conversion, systematic experiments are being conducted since the early 1960s and several more decades of experimentation are required. Change of springs and dampers is time consuming and requires frequent recalibration. Emulating springs and dampers with a controller makes parameter change efficient and accurate. There are two approaches to this problem: The first involves the hydrodynamic force in the closed-loop and is easier to implement. The second called virtual damping and spring (Vck) does not involve the hydrodynamic force in the closed-loop but requires an elaborate system identification (SI) process. Vck was developed in the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan for the first time in 2009 and resulted in extensive data generation. In this paper, the second generation of Vck is developed and validated by comparison of the FIM experiments between a Vck emulated oscillator and an oscillator with physical springs and dampers. The main findings are: (a) the Vck system developed keeps the hydrodynamic force out of the control-loop and, thus, does not bias the FIM, (b) The controller-induced lag is minimal and significantly reduced compared to the first generation of Vck built in the MRELab due to use of an Arduino embedded board to control a servomotor instead of Labview, (c) The SI process revealed a static, third-order, nonlinear viscous model but no need for dynamic terms with memory, and (d) The agreement between real and virtual springs and dampers is excellent in FIM including vortex-induced vibrations (VIVs) and galloping measurements over the entire range of spring constants and velocities tested (16,000 < Re < 140,000).

Hydrokinetic Energy Conversion by Flow-Induced Oscillation of Two Tandem-Cylinders of Different Stiffness

2020 ◽  
Author(s):  
Wenyong Yuan ◽  
Hai Sun ◽  
Nicholas Beltsos ◽  
Michael M. Bernitsas
Keyword(s):  
Structural Parameters ◽  
Damping Ratio ◽  
Great Influence ◽  
Clean Energy ◽  
Shielding Effect ◽  
Ocean Current ◽  
Vortex Induced Vibration ◽  
Hydrokinetic Energy ◽  
Energy Harnessing ◽  
The Impact

Abstract The VIVACE (Vortex-Induced Vibration for Aquatic Clean Energy) Converter harnesses hydrokinetic energy by enhancing flow-induced oscillations (FIOs) of elastically supported rigid cylinders in a river, tide, or ocean current. The harnessing power depends on the intensity of the oscillation, which is a consequence of the flow-structure interaction. The inflow condition for the downstream (2nd) cylinder is slowed down and perturbed by the upstream (1st) cylinder, due to the shielding effect. Therefore, the optimal structural parameters, i.e., stiffness and damping ratio, for the 2nd cylinder may be different from the 1st cylinder, in terms of energy harnessing. To improve the performance of the VIVACE Converter, a series of experiments are conducted in a recirculating water channel, with various stiffness combinations of two cylinders in tandem. Three center-to-center spacings, six damping ratios, and seven combinations of spring stiffness are tested. The stiffness of the 1st cylinder, K1, is 600 N/m or 1,000 N/m, while the stiffness of the 2nd cylinder, K2, varies from 400 N/m to 1,200 N/m in increments of 200N/m. Results show that K2 does not affect the energy harnessing power in vortex-induced vibration (VIV) occurring at low speeds, but has great influence on the harnessing power at higher velocities in the transition region from VIV to galloping and in galloping. Decreasing K2 onsets and enhances galloping at lower flow velocity and harnesses up to 110% more energy than the case of K1 = K2. For K1 = 1,000 N/m, the harnessed power is the same for all the combinations of K1 and K2. The overall performance is best when K1 = K2. As spacing increases, the impact of K2 is diminished as explain by the dependence of power on the amplitude and frequency of cylinder oscillations.

Nonlinear Piecewise Restoring Force in Hydrokinetic Power Conversion Using Flow-Induced Vibrations of Two Tandem Cylinders

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Chunhui Ma ◽  
Hai Sun ◽  
Marinos M. Bernitsas
Keyword(s):  
Positive Impact ◽  
Clean Energy ◽  
Circular Cylinders ◽  
University Of Michigan ◽  
Restoring Force ◽  
Nonlinear Spring ◽  
Hydrokinetic Energy ◽  
Spacing Ratio ◽  
Flow Induced Vibrations ◽  
The University

Flow-induced vibrations (FIVs) of two tandem, rigid, circular cylinders with piecewise continuous restoring force are investigated for Reynolds number 24,000 ≤ Re ≤ 120,000 with damping, and restoring force function as parameters. Selective roughness is applied to enhance FIV and increase the hydrokinetic energy captured by the vortex-induced vibration for aquatic clean energy (VIVACE) converter. Experimental results for amplitude response, frequency response, interactions between cylinders, energy harvesting, and efficiency are presented and discussed. All experiments were conducted in the low-turbulence free-surface water (LTFSW) Channel of the MRELab of the University of Michigan. The main conclusions are as follows: (1) the nonlinear-spring converter can harness energy from flows as slow as 0.33 m/s with no upper limit; (2) the nonlinear-spring converter has better performance at initial galloping than its linear-spring counterpart; (3) the FIV response is predominantly periodic for all nonlinear spring functions used; (4) the influence from the upstream cylinder is becoming more dominant as damping increases; (5) optimal power harnessing is achieved by changing the linear viscous damping and tandem spacing L/D; (6) close spacing ratio L/D = 1.57 has a positive impact on the harnessed power in VIV to galloping transition; and (7) the interactions between two cylinders have a positive impact on the upstream cylinder regardless of the spacing and harness damping.

Bio-Inspired Coupling of Camber and Sweep in Morphing Wings

2016 ◽  
Author(s):  
Amin Moosavian ◽  
Lawren L. Gamble ◽  
Alexander M. Pankonien ◽  
Daniel J. Inman
Keyword(s):  
Wind Tunnel ◽  
Flow Speed ◽  
Navier Stokes ◽  
University Of Michigan ◽  
Wind Tunnel Experiments ◽  
Reynolds Number Flow ◽  
Morphing Wings ◽  
Number Flow ◽  
3D Printed ◽  
The University

This work aims to investigate how bio-inspired morphing wings built with state-of-the-art materials affect the aerodynamics and extend the range of flight conditions. In particular, this study investigates the aerodynamic effects of coupled airfoil and planform sweep morphing. The morphed geometries were chosen to resemble a current morphing design that uses Macro Fiber Composites (MFCs) and Shape Memory Alloy (SMA) wires. The primary mode of camber actuation is achieved using the MFCs which are supplemented using antagonistic SMA wires, forming a hinge ahead of the MFCs. The SMA hinge also allows for bi-directional actuation, resulting in a reflexed airfoil. Numerical simulations were conducted using a Reynolds-averaged-Navier-Stokes (RANS) turbulence model for low-Reynolds-number flow, in addition to wind tunnel experiments. Nine different wing configurations were considered consisting of combinations of 3 sweep angles and 3 airfoil profiles, including unactuated (baseline), monotonic camber actuation, and reflex actuation. These geometries were 3D printed on a high resolution printer. Tests were conducted in a 2 ft. × 2 ft. wind tunnel at the University of Michigan at a flow speed of 10 m/s, consistent with the flow regime expected for this scale of aircraft. The preliminary results suggest a definite improvement in flight performance associated with the proposed coupling.

scholarly journals Prediction of Dynamic Responses of Flow-Induced Vibration Using Deep Learning

2021 ◽  
Vol 11 (15) ◽  
pp. 7163
Author(s):  
Gi-yong Kim ◽  
Chaeog Lim ◽  
Eun Soo Kim ◽  
Sung-chul Shin
Keyword(s):  
Experimental Data ◽  
Electrical Energy ◽  
Clean Energy ◽  
Flow Speed ◽  
Dynamic Responses ◽  
University Of Michigan ◽  
Flow Induced Vibration ◽  
Marine Renewable Energy ◽  
The University ◽  
Good Agreement

Flow-induced vibration (FIV) is a phenomenon in which the flow passing through a structure exerts periodic forces on the structure. Most studies on FIVs focus on suppressing this phenomenon. However, the Marine Renewable Energy Laboratory (MRELab) at the University of Michigan, USA, has developed a technology called the vortex-induced vibration for aquatic clean energy (VIVACE) converters that reinforces FIV and converts the energy in tidal currents to electrical energy. This study introduces the experimental data of the VIVACE converter and the associated method using deep neural networks (DNNs) to predict the dynamic responses of the converter. The DNN was trained and verified with experimental data from the MRELab, and the findings show that the amplitudes and frequencies of a single cylinder in the FIV predicted by the DNN under various test conditions were in good agreement with the experimental data. Finally, based on both the predicted and experimental data, the optimal power envelope of the VIVACE converter was generated as a function of the flow speed. The predictions using DNNs are expected to be more accurate as they can be trained with more experimental data in the future and will help to substantially reduce the number of experiments on FIVs.

Computational and Experimental Assessment of Turbulence Stimulation on Flow Induced Motion of Circular Cylinder

2015 ◽  
Author(s):  
Omer Kemal Kinaci ◽  
Sami Lakka ◽  
Hai Sun ◽  
Michael M. Bernitsas
Keyword(s):  
Parametric Design ◽  
Fluid Dynamic ◽  
Circular Cylinders ◽  
Design Parameters ◽  
Turbulence Control ◽  
Hydrokinetic Energy ◽  
Flow Features ◽  
Induced Motion ◽  
Marine Hydrokinetic ◽  
The University

In the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan, Flow Induced Motion (FIM) is studied as a means to convert marine hydrokinetic energy to electricity using the VIVACE energy harvester [1–4]. Turbulence stimulation in the form of sand-strips, referred to as Passive Turbulence Control (PTC), were added to oscillating cylinders in 2008 [5]. PTC enabled VIVACE to harness hydrokinetic energy from currents/tides over the entire range of FIM including VIV and galloping. In 2011, the MRELab produced experimentally the PTC-to-FIM Map defining the induced cylinder motion based on the location of PTC [6]. In 2013, the robustness of the map was tested and dominant zones were identified [7]. Even though the PTC-to-FIM Map has become a powerful tool in inducing specific motions of circular cylinders, several parameters remain unexplored. Experiments, though the ultimate verification tool, are time consuming and hard to provide all needed information. A computational tool that could predict the FIM of a cylinder correctly would be invaluable to study the full parametric design space. A major side-benefit of PTC was the fact that PTC enabled computational fluid dynamic (CFD) simulations to generate results in good agreement with experiments by forcing the location of the separation point [8]. This valuable tool, along with experiments, is used in this paper to investigate PTC design parameters such as width and thickness and their impact on flow features with the intent of maximizing FIM and, thus, hydrokinetic energy conversion.

Hydrokinetic Energy Conversion by Flow-Induced Oscillation of Two Tandem-Cylinders of Different Stiffness

2021 ◽  
pp. 1-17
Author(s):  
Wenyong Yuan ◽  
Hai Sun ◽  
Eun Soo Kim ◽  
H Li ◽  
Nicholas Beltsos ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Damping Ratio ◽  
Water Channel ◽  
Great Influence ◽  
Clean Energy ◽  
Shielding Effect ◽  
Ocean Current ◽  
Vortex Induced Vibration ◽  
Hydrokinetic Energy ◽  
Energy Harnessing

Abstract The VIVACE (Vortex-Induced Vibration for Aquatic Clean Energy) Converter harnesses hydrokinetic energy by enhancing flow-induced oscillations (FIOs) of elastically supported rigid cylinders in a river, tide, or ocean current. The harnessing power depends on the intensity of the oscillation, which is a consequence of the flow-structure interaction. The inflow condition for the downstream (2nd) cylinder is slowed down and perturbed by the upstream (1st) cylinder, due to the shielding effect. Therefore, the optimal structural parameters, i.e., stiffness and damping ratio, for the 2nd cylinder may be different from the 1st cylinder, in terms of energy harnessing. To improve the performance of the VIVACE Converter, a series of experiments are conducted in a recirculating water channel, with various stiffness combinations of two cylinders in tandem. Results show that the stiffness of the 2nd cylinder, K2, does not affect the energy harnessing power in vortex-induced vibration (VIV) occurring at low speeds, because the oscillation of the downstream cylinder in this velocity range is completely dominated by the wake of the upstream cylinder. K2 has a great influence on the harnessing power at higher velocities in the transition region from VIV to galloping and in galloping. Changing K2 onsets and enhances galloping at lower flow velocity and harnesses up to 110% more energy than the case of K1 = K2.

Nonlinear Piecewise Restoring Force in Hydrokinetic Power Conversion Using Flow Induced Motions of Two Tandem Cylinders

2017 ◽  
Author(s):  
Chunhui Ma ◽  
Hai Sun ◽  
Marinos M. Bernitsas
Keyword(s):  
Positive Impact ◽  
Clean Energy ◽  
Circular Cylinders ◽  
University Of Michigan ◽  
Restoring Force ◽  
Nonlinear Spring ◽  
Hydrokinetic Energy ◽  
Spacing Ratio ◽  
Linear Spring ◽  
The University

Flow Induced Motions (FIMs) of two tandem, rigid, circular cylinders with piecewise continuous restoring force are investigated for Reynolds number 24,000≤Re≤120,000 with damping, and restoring force function as parameters. Selective roughness is applied to enhance FIM and increase the hydrokinetic energy captured by the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) Converter. Experimental results for amplitude response, frequency response, interactions between cylinders, energy harvesting, and efficiency are presented and discussed. All experiments were conducted in the Low Turbulence Free Surface Water (LTFSW) Channel of the MRELab of the University of Michigan. The main conclusions are: (1) The nonlinear-spring, Converter can harness energy from flows as slow as 0.33 m/s with no upper limit. (2) The nonlinear-spring Converter has better performance at initial galloping than its linear-spring counterpart. (3) The FIM response is predominantly periodic for all nonlinear spring functions used. (4) The influence from the upstream cylinder is becoming more dominant as damping increases. (5) Optimal power harnessing is achieved by changing the linear viscous damping and tandem spacing L/D. (6) Close spacing ratio L/D = 1.57 has a positive impact on the harnessed power in VIV to galloping transition. (7) The interactions between two cylinders have a positive impact on the upstream cylinder regardless of the spacing and harness damping.

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