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.

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.

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.

The VIVACE Converter: Model Tests at High Damping and Reynolds Number Around 105

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Michael M. Bernitsas ◽  
Y. Ben-Simon ◽  
Kamaldev Raghavan ◽  
E. M. H. Garcia
Keyword(s):  
Reynolds Number ◽  
Renewable Energy ◽  
Early Stage ◽  
Water Channel ◽  
Fluid Flows ◽  
Clean Energy ◽  
Vortex Induced Vibration ◽  
Stage Of Development ◽  
Vortex Induced Vibrations ◽  
The University

The vortex induced vibrations for aquatic clean energy (VIVACE) converter is a new concept to generate clean and renewable energy from fluid flows such as those abundant in oceans, rivers, or other water resources. The underlying concepts for design, scaling, and operation of VIVACE were introduced in Bernitsas et al., 2008, “VIVACE (Vortex Induced Vibration Aquatic Clean Energy): A New Concept in Generation of Clean and Renewable Energy From Fluid Flow,” ASME J. Offshore Mech. Arct. Eng., 130(4), p. 041101. In its simplest form, a VIVACE modulo consists of a single rigid cylinder mounted on elastic supports and connected to a power takeoff (PTO) system. The cylinder is placed in a steady unidirectional current and excited in vortex induced vibration (VIV). In this paper, the VIVACE modulo was tested in the Low Turbulence Free-Surface Water Channel of the University of Michigan to demonstrate the concept, generate electricity, measure the power out, and calculate basic benchmarking measures such as energy density. The tests performed were tailored to the particulars of the VIVACE modulo, which dictate that the cylinder operate in VIV under high damping and as high a Reynolds number as possible. At the same time, a broad range of synchronization is required to make VIVACE effective in energy generation in a realistic environment. Due to these requirements, VIV tests have not been performed before in the subspace applicable to the operation of the VIVACE modulo. In the process of extracting fluid kinetic energy and converting it to electricity in the laboratory, for a given set of cylinder-springs-transmission-generator, only the damping used for harnessing electricity was optimized. Even at this early stage of development, for the tested VIVACE modulo, the maximum peak power achieved was Ppeak=0.308×12ρDLL. The corresponding integrated power in that particular test was PVIVACE=0.22×12ρU3DL with theoretical upper limit based on measurements of PUL–VIVACE=0.3663. Such power was achieved at velocity U=0.840m∕s=1.63Kn.

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.

Enhancement of High Damping VIV Through Roughness Distribution for Energy Harnessing at 8×103 < Re < 1.5×105

2008 ◽  
Author(s):  
Kamaldev Raghavan ◽  
Michael M. Bernitsas
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Renewable Energy ◽  
Clean Energy ◽  
Reynolds Numbers ◽  
Experimental Facility ◽  
Energy Converter ◽  
High Lift ◽  
Energy Harnessing

Vortex Induced Vibration (VIV) of a circular cylinder in a steady flow is enhanced using distributed surface roughness. VIV enhancement is needed in harnessing clean and renewable energy from ocean/river currents using the VIVACE (VIV for Aquatic Clean Energy) Converter (Bernitsas et al. 2006a, 2006b; Raghavan et al. 2007). High damping is mandatory in energy harnessing and higher Reynolds numbers are required to reach the high lift TrSL3 regime. Roughness is added to the surface of the cylinder in the form of sandpaper strips to achieve three goals: (1) Trip separation in a controlled manner. (2) Fully correlate the flow regardless of the Reynolds number regime. (3) Energize the boundary layer, thus inducing higher vorticity and circulation and consequently lift. Our experiments show that it is possible to achieve all three goals and reach VIV amplitudes of 2.1 to 2.7 diameters under high damping. The range of synchronization increased dramatically but its end was not observed within the capabilities of our experimental facility.

Vortex Induced Vibration for Aquatic Clean Energy

2011 ◽  
Vol 110-116 ◽  
pp. 2117-2117
Keyword(s):  
Clean Energy ◽  
Vortex Induced Vibration ◽  
International Conference ◽  
Asme Journal ◽  
Energy Harnessing

Removed due to plagiarism. Original published: ENHANCEMENT OF HIGH DAMPING VIV THROUGH ROUGHNESS DISTRIBUTION FOR ENERGY HARNESSING AT 8×103 < Re < 1.5×105 Kamaldev Raghavan, Michael M. Bernitsas Proceedings of the ASME 27th International Conference on Offshore Mechanics and Arctic Engineering OMAE2008, June 15-20, 2008, Estoril, Portugal Publihsed By ASME Journal of Offshore Mechanics and Arctic Engineering 041101 Vol. 130, NOVEMBER 2008 Michael M. Bernitsas et al. Published By ASME

III. Recent Works on Medieval, Turkish and Modern Greece

1928 ◽  
Vol 2 (03) ◽  
pp. 229-247 ◽  
Author(s):  
William Miller
Keyword(s):  
New York ◽  
Present Article ◽  
University Of Michigan ◽  
Modern History ◽  
Greek History ◽  
General Field ◽  
History Of ◽  
Modern Greece ◽  
The University ◽  
First Time

I propose in the present article to mention the additions which have been made during recent years to our knowledge of the medieval, Turkish and modern periods of Greek history, especially by the Greeks themselves. In the fifth edition of Paparregopoulos' standardHistory of the Greek Nation, edited and continued by Professor P. Karolides, we have an account of the whole history of the Greeks from prehistoric times down to the annexation of Thessaly and Arta in 1881. The editor, who sat in the Turkish parliament and is particularly strong in all that regards the Moslem world, has, by large additions to the text and by footnotes, brought the classic masterpiece of his author up to date, while for the first time this work is illustrated and indexed. In the general field of medieval Greek history theAnnual of the Society of Byzantine Studies, which first appeared in 1924, has published a number of articles by Greek specialists, while theByzantinisch-Neugriechische Jahrbücherof Professor Nikos A. Bees, started at Berlin in 1920, has been published since 1926 in Athens, where a similar periodical,Helleniká, edited by Professors Amantos and Kougeas, is announced. The local medieval and modern history of Epeiros is being collected in theEpeirote Chronicles, of which two volumes and a biographical supplement have appeared; that of Thrace in the similar periodical,Thrakiká, of which one complete volume has been issued. Dr Franz Dölger has produced two instalments of theCorpus der griechischen Urkunden des Mittelalters und der neueren Zeit, planned by Krumbacher, and giving German summaries of documents from 565 to 1204, andBeiträge zur Geschichte der byzantinischen Finanzverwaltung besonders des10.und11.Fahrhunderts. Messrs A. E. R. Boak and James E. Dunlap have contributedTwo Studies in Later Roman and Byzantine Administrationon “The Master of the Offices” and “The Office of the Grand Chamberlain” respectively toThe University of Michigan Studies, Humanistic Series(vol. XIV, New York, 1924).

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.

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.

The International Congress of Orientalists

1968 ◽  
Vol 2 (2) ◽  
pp. 15-20
Author(s):  
Stanford J. Shaw
Keyword(s):  
United States ◽  
Considerable Increase ◽  
The United States ◽  
Western Hemisphere ◽  
International Congress ◽  
University Of Michigan ◽  
Ann Arbor ◽  
Oriental Studies ◽  
The University ◽  
First Time

The XXVII International Congress of Orientalists was held at the University of Michigan, Ann Arbor, Michigan, from August 13 through August 19, 1967. This was the first time the Congress was held in the United States or, for that matter, in the Western Hemisphere. Before the Congress convened, fears were expressed that the distance of Ann Arbor from the East Coast of the United States, and that of the United States from the older centers of Oriental studies, would appreciably reduce attendance. In fact, however, more than 2500 scholars attended, a considerable increase over the previous Congress, demonstrating the tremendous development of Oriental studies in the United States during the previous two decades, and also the effectiveness of the Organizing Committee’s effort to assist the transportation of foreign scholars by means of subsidized airplane flights from Tokyo as well as principal centers in Europe.

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