scholarly journals The Effects of Reynolds Number on Energy Harvesting from FIV by a Square Cylinder

2020 ◽  
Vol 38 (5) ◽  
pp. 928-936
Author(s):  
Peng Han ◽  
Guang Pan ◽  
Qiaogao Huang ◽  
Yao SHI
Keyword(s):  
Reynolds Number ◽  
Energy Harvesting ◽  
Energy Conversion ◽  
Reynolds Numbers ◽  
Energy Conversion Efficiency ◽  
Published Data ◽  
Square Cylinder ◽  
A Value ◽  
Vibration Responses ◽  
Intense Vibration

Under the action of incoming flow, the square cylinder can generate more intense vibration responses than the circular cylinder, which is beneficial for energy harvesting. Numerical simulations for FIV of the square-cylinder energy conversion system are carried out. URANS equations are used in conjunction with the shear stress transport k-ω turbulence model to predict the flow, and the equations for vibrations are solved by the Newmark-β algorithm. The present numerical method is validated against the published data with good consistency. The Reduced velocity Ur is varied from 1-20, with corresponding Reynolds numbers of 24 000-160 000. The numerical results indicate that the Reynolds number significantly affects the frequency response, amplitude response, vortex shedding mode, and energy conversion efficiency. The highest efficiency point locates at Re=88 000, with a value of 7.156%. When Re>120 000, the system transits from vortex-induced vibration into galloping, and its vibration responses as well as energy harvesting characteristics change sharply. Fully developed galloping motion occurs when Re>144 000.

scholarly journals Influence of attack angle on vortex-induced vibration and energy harvesting of two cylinders in side-by-side arrangement

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401882259
Author(s):  
Li Zhang ◽  
Xinru Mao ◽  
Lin Ding
Keyword(s):  
Energy Harvesting ◽  
Energy Conversion ◽  
Energy Conversion Efficiency ◽  
Maximum Energy ◽  
Attack Angle ◽  
Navier Stokes ◽  
Vortex Induced Vibration ◽  
Hydrokinetic Energy ◽  
Wake Patterns ◽  
Vibration Responses

The vortex-induced vibration and energy harvesting of two cylinders in side-by-side arrangement with different attack angles are numerically investigated using two-dimensional unsteady Reynolds-Averaged Navier–Stokes simulations. The Reynolds number ranges from 1000 to 10,000, and the attack angle of free flow is varied from 0° to 90°. Results indicate that the vortex-induced vibration responses with attack angle range of 0°≤  α ≤ 30° are stronger than other attack angle cases. The parallel vortex streets are clearly observed with synchronized vortex shedding. Relatively large attack angle leads to a phase difference between the wake patterns of the two cylinders. Hydrokinetic energy can be obviously harvested when Re > 4000. Compared with the larger attack angle case, the two side-by-side cylinders with smaller attack angle have better performance on energy conversion. The maximum energy conversion efficiency of 21.7% is achieved. The optimum region for energy conversion is 5000 ≤  Re ≤ 7000 and 0°≤  α ≤ 30°.

Empirical Estimates of Body Drag of Large Waterfowl and Raptors

1988 ◽  
Vol 135 (1) ◽  
pp. 253-264 ◽  
Author(s):  
C. J. PENNYCUICK ◽  
HOLLIDAY H. OBRECHT ◽  
MARK R. FULLER
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
The Body ◽  
Number Range ◽  
Empirical Estimates ◽  
A Value ◽  
Body Drag ◽  
Wind Tunnel Measurements ◽  
Large Living ◽  
Performance Estimates

To whom reprint requests should be addressed. Measurements of the body frontal area of some large living waterfowl (Anatidae) and raptors (Falconiformes) were found to vary with the two-thirds power of the body mass, with no distinction between the two groups. Wind tunnel measurements on frozen bodies gave drag coefficients ranging from 0.25 to 0.39, in the Reynolds number range 145 000 to 462 000. Combining these observations with those of Prior (1984), which extended to lower Reynolds numbers, a practical rule is proposed for choosing a value of the body drag coefficient for use in performance estimates.

scholarly journals Analysis and optimal design of a vibration isolation system combined with electromagnetic energy harvester

2019 ◽  
Vol 30 (16) ◽  
pp. 2382-2395
Author(s):  
Uchenna Diala ◽  
SM Mahdi Mofidian ◽  
Zi-Qiang Lang ◽  
Hamzeh Bardaweel
Keyword(s):  
Energy Harvesting ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Vibration Isolation ◽  
Energy Conversion Efficiency ◽  
Isolation System ◽  
Magnetic Components ◽  
Energy Harvesting System ◽  
Response Function Method ◽  
Conversion Efficiencies

This work investigates a vibration isolation energy harvesting system and studies its design to achieve an optimal performance. The system uses a combination of elastic and magnetic components to facilitate its dual functionality. A prototype of the vibration isolation energy harvesting device is fabricated and examined experimentally. A mathematical model is developed using first principle and analyzed using the output frequency response function method. Results from model analysis show an excellent agreement with experiment. Since any vibration isolation energy harvesting system is required to perform two functions simultaneously, optimization of the system is carried out to maximize energy conversion efficiency without jeopardizing the system’s vibration isolation performance. To the knowledge of the authors, this work is the first effort to tackle the issue of simultaneous vibration isolation energy harvesting using an analytical approach. Explicit analytical relationships describing the vibration isolation energy harvesting system transmissibility and energy conversion efficiency are developed. Results exhibit a maximum attainable energy conversion efficiency in the order of 1%. Results suggest that for low acceleration levels, lower damping values are favorable and yield higher conversion efficiencies and improved vibration isolation characteristics. At higher acceleration, there is a trade-off where lower damping values worsen vibration isolation but yield higher conversion efficiencies.

scholarly journals Design and dynamic analysis of integrated architecture for vibration energy harvesting including piezoelectric frame and mechanical amplifier

2021 ◽  
Author(s):  
Xiangjian Duan ◽  
Dongxing Cao ◽  
Xiaoguang Li ◽  
Yongjun Shen
Keyword(s):  
Energy Harvesting ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Structural Parameters ◽  
Energy Conversion Efficiency ◽  
High Energy ◽  
Ambient Vibration ◽  
Vibration Energy ◽  
Variable Cross ◽  
Mechanical Amplification

AbstractVibration energy harvesters (VEHs) can transform ambient vibration energy to electricity and have been widely investigated as promising self-powered devices for wireless sensor networks, wearable sensors, and applications of a micro-electro-mechanical system (MEMS). However, the ambient vibration is always too weak to hinder the high energy conversion efficiency. In this paper, the integrated frame composed of piezoelectric beams and mechanical amplifiers is proposed to improve the energy conversion efficiency of a VEH. First, the initial structures of a piezoelectric frame (PF) and an amplification frame (AF) are designed. The dynamic model is then established to analyze the influence of key structural parameters on the mechanical amplification factor. Finite element simulation is conducted to study the energy harvesting performance, where the stiffness characteristics and power output in the cases of series and parallel load resistance are discussed in detail. Furthermore, piezoelectric beams with variable cross-sections are introduced to optimize and improve the energy harvesting efficiency. Advantages of the PF with the AF are illustrated by comparison with conventional piezoelectric cantilever beams. The results show that the proposed integrated VEH has a good mechanical amplification capability and is more suitable for low-frequency vibration conditions.

Resistance and Fluctuating Pressures of a Large Elbow in High Reynolds Numbers

2006 ◽  
Vol 128 (5) ◽  
pp. 1063-1073 ◽  
Author(s):  
Tadashi Shiraishi ◽  
Hisato Watakabe ◽  
Hiromi Sago ◽  
Mamoru Konomura ◽  
Akira Yamaguchi ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pipe Wall ◽  
Reynolds Numbers ◽  
Resistance Coefficient ◽  
Scale Model ◽  
Published Data ◽  
Energy Agency ◽  
Fluctuating Pressure ◽  
High Reynolds ◽  
Flow Separation And Reattachment

For the Japan Atomic Energy Agency sodium-cooled fast reactor, an experimental study on the fluctuating pressure of the hot legs was carried out with tests in a 1/3-scale model. The total resistance coefficient is consistent with published data, and, additionally, our research has given data up to the Reynolds number of 8.0×106. The flow visualization and velocity measurement confirmed the independence of the flow on the Reynolds number. Pressures on the pipe wall were statistically examined to predict the characteristics of fluctuating pressures of the hot legs. It reveals that generation of fluctuating pressure is dominant on the boundary of flow separation and reattachment.

scholarly journals Modeling and Control of Lozenge-Shaped Dielectric Elastomer Generators

2013 ◽  
Author(s):  
Giacomo Moretti ◽  
Marco Fontana ◽  
Rocco Vertechy
Keyword(s):  
Energy Harvesting ◽  
Energy Conversion ◽  
Low Cost ◽  
Failure Criteria ◽  
Energy Conversion Efficiency ◽  
Cycle Frequency ◽  
Modeling And Control ◽  
Energy Conversion Systems ◽  
Hyper Elastic ◽  
A Charge

Dielectric Elastomers (DEs) are a very promising technology for the development of energy harvesting devices based on the variable-capacitance electrostatic generator principle. As compared to other technologies, DE Generators (DEGs) are solid-state energy conversion systems which potentially feature: 1) large energy densities, 2) good energy conversion efficiency that is rather independent of cycle frequency, 3) easiness of manufacturing and assembling, 4) high shock resistance, 5) silent operation, 6) low cost. Envisioned applications for DEGs are in devices that convert ocean wave energy into usable electricity. This paper introduces the Lozenge-Shaped DEG (LS-DEG) that is a specific type of planar DE transducer with one degree of freedom. A LS-DEG consists of a planar DE membrane that is connected along its perimeter to the links of a parallelogram four-bar mechanism. As the mechanism is put into reciprocal motion, the DE membrane varies its capacitance that is then employed as a charge pump to convert external mechanical work into usable electricity. Specifically, this paper describes the functioning principle of LS-DEGs, and provides a comparison between different hyper-elastic models that can be used to predict the energy harvesting performances of realistic prototypes. Case studies are presented which address the constrained optimization of LS-DEGs subjected to failure criteria and practical design constraints.

Flow and Heat Transfer of Nanoencapsulated Phase Change Material Slurry Past a Unconfined Square Cylinder

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Hamid Reza Seyf ◽  
Michael R. Wilson ◽  
Yuwen Zhang ◽  
H. B. Ma
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Phase Change ◽  
Melting Temperature ◽  
Base Fluid ◽  
Volume Fraction ◽  
Pure Water ◽  
Reynolds Numbers ◽  
Square Cylinder ◽  
Change Material

Numerical solution is carried out to analyze the effect of nanoencapsulated phase change material (NEPCM) slurry on forced convection heat transfer of steady laminar flow past an isothermal square cylinder. The base fluid is water while the NEPCM particles material is n-octadecane with an average diameter of 100 nm. A parametric study was performed for different volume fraction of nanoparticles ranging from 0% to 30%, two melting temperature ranges, i.e., 10 K and 20 K, and different inlet Reynolds numbers ranging from 15 to 45. The governing equations of flow and energy are solved simultaneously using a finite volume method (FVM) on collocated grid arrangement. It was found that for both NEPCM slurry and pure water, local and average heat transfer coefficients increases with increasing Reynolds number. The results of heat transfer characteristics of slurry flow over the square cylinder showed remarkable enhancement relative to that of the base fluid. The enhancement intensifies for higher particle volume concentrations and higher Reynolds numbers. However, utilizing the slurry can cause higher shear stress on the wall due to higher viscosity of mixture compared to the pure water. The melting temperature range of NEPCM particles has slight effect on heat transfer, although with increasing volume fraction and Reynolds number, lower melting range leads to higher heat transfer coefficient.

2D WS2 Embedded PVDF Nanocomposites for Photosensitive Piezoelectric Nanogenerators with a Colossal Energy Conversion Efficiency ~ 25.6%

Nanoscale ◽  
2021 ◽  
Author(s):  
Didhiti Bhattacharya ◽  
Sayan Bayan ◽  
Rajib K Mitra ◽  
Samit K Ray
Keyword(s):  
Renewable Energy ◽  
Energy Harvesting ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Low Cost ◽  
Energy Conversion Efficiency ◽  
Light Weight ◽  
Piezoelectric Nanogenerators

Benefited with the advantage of low cost, light weight and mechanical flexibility, piezoelectric nanogenerators have potential for applications in renewable energy harvesting from various unexplored sources. Here we report the...

scholarly journals Optimizing energy harvesting performance of silicone elastomers by molecular grafting of azobenzene to the macromolecular network

RSC Advances ◽  
2021 ◽  
Vol 11 (31) ◽  
pp. 19088-19094
Author(s):  
Min Gong ◽  
Feilong Song ◽  
Hejian Li ◽  
Xiang Lin ◽  
Jiaping Wang ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Silicone Rubber ◽  
Polymer Network ◽  
Energy Conversion Efficiency ◽  
Silicone Elastomers ◽  
The Matrix ◽  
Macromolecular Network

Homogeneous silicone rubber was prepared for DEG applications by molecular grafting of azobenzene to the polymer network. The energy conversion efficiency of the composite was optimized to 5.01%, increased by 150% compared to the matrix.

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