scholarly journals Parametric CFD study of micro-energy harvesting in a flow channel exploiting vortex shedding

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Dimitrios G. Koubogiannis
Keyword(s):  
Energy Harvesting ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Electrical Power ◽  
Bluff Bodies ◽  
Miniature Device ◽  
Parametric Studies ◽  
Body Shapes ◽  
Duration Of Operation ◽  
Energy Harvesting Devices

Abstract Miniature energy harvesting devices are increasingly used in various fields. For example, Wireless Sensor Networks have recently made great progress in many applications. However, their main drawback, i.e. the limited duration of operation, poses the requirement for an effective way to recharge their batteries. In this context, the presentwork focuses on the study of micro-energy harvesting from flow by exploiting vortex shedding behind bluff bodies, in order to cause oscillations to a piezoelectric film and generate the required electrical power. To this end, a Computational Fluid Dynamics (CFD) tool is validated on a particular miniature device configuration proposed in the literature and implemented for the numerical simulations of flow around bluff micro-bodies in a very small channel. Aiming to enhance vortex shedding, parametric studies corresponding to different bluff body shapes and arrangements for a fixed Reynolds number are performed, the main parameters involved in the phenomenon are highlighted and the potential for vortex shedding exploitation is qualitatively assessed.

Vortex Shedding in a Linear Shear Flow From a Vibrating Marine Cable With Attached Bluff Bodies

1985 ◽  
Vol 107 (1) ◽  
pp. 61-66 ◽  
Author(s):  
R. D. Peltzer ◽  
D. M. Rooney
Keyword(s):  
Shear Flow ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Bluff Bodies ◽  
Near Wake ◽  
Cable System ◽  
Sheared Flow ◽  
Linear Shear ◽  
Body Shapes ◽  
Marine Cable

The present study examines the vortex street wake behavior of a flexible, helically wound, high aspect ratio marine cable in a linear shear flow. Particular attention is paid to the lock-on phenomena associated with uniform and sheared flow past the cable when it is forced to vibrate in the first mode, normal to the flow. An analysis is given of the effects on the vortex shedding and synchronization phenomena that are generated by placing distributions of spherical bluff body shapes along the span of the cable in uniform and sheared flow. The latter geometry is representative of a number of cable system deployments and has special consequencies for strumming in a shear flow. The effectiveness of these attached spheres as strumming-suppression devices is evaluated. Synchronized vibration and/or the presence of the bluff bodies significantly affected the spanwise character of the near wake cellular vortex shedding structure. The spanwise extent of the resonant, vortex-excited oscillations was significantly extended by the presence of the spheres along the cable span. This finding was particularly significant because it meant that the undesirable effects that accompanied synchronization would be extended over a longer portion of the cable span.

Vortex shedding from bluff bodies in a shear flow

1973 ◽  
Vol 60 (2) ◽  
pp. 401-409 ◽  
Author(s):  
D. J. Maull ◽  
R. A. Young
Keyword(s):  
Shear Flow ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Pressure Coefficient ◽  
Uniform Flow ◽  
Base Pressure ◽  
Longitudinal Vortex ◽  
Bluff Bodies ◽  
Stream Direction

Experiments are described in which the vortex shedding from a bluff body and the base pressure coefficient have been measured in a shear flow. It is shown that the shedding breaks down into a number of spanwise cells in each of which the frequency is constant. The division between the cells is thought to be marked by a longitudinal vortex in the stream direction and this is supported by evidence from experiments where a longitudinal vortex was generated in an otherwise uniform flow.

Vortex shedding from bluff bodies in oscillatory flow: A report on Euromech 119

1980 ◽  
Vol 99 (2) ◽  
pp. 225-245 ◽  
Author(s):  
P. W. Bearman ◽  
J. M. R. Graham
Keyword(s):  
Vortex Shedding ◽  
Oscillatory Flow ◽  
Bluff Body ◽  
Circular Cylinders ◽  
Bluff Bodies ◽  
Unidirectional Flow ◽  
Low Reynolds Number Flows ◽  
Wide Range ◽  
Bluff Body Flow ◽  
Reynolds Number Flows

European Mechanics Colloquium number 119 was held at Imperial College on 16–18 July 1979, when the subject of vortex shedding from bodies in unidirectional flow and oscillatory flow, was discussed. A wide range of experimental work was presented including low-Reynolds-number flows around circular cylinders, the influence of disturbances on bluff body flow, the measurement of fluctuating forces and the influence of oscillations of the stream. About a third of the 33 papers presented concentrated on theoretical aspects and the majority of these were concerned with the ‘method of discrete vortices’.

scholarly journals Footstep Energy Harvesting with the Magnetostrictive Fiber Integrated Shoes

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2055 ◽  
Author(s):  
Hiroki Kurita ◽  
Kenichi Katabira ◽  
Yu Yoshida ◽  
Fumio Narita
Keyword(s):  
Energy Harvesting ◽  
Piezoelectric Materials ◽  
Electrical Power ◽  
Point Of View ◽  
Output Energy ◽  
User Mobility ◽  
Magnetostrictive Materials ◽  
Long Time ◽  
Functional Point ◽  
Energy Harvesting Devices

Wearable energy harvesting devices attract attention as the devices provide electrical power without inhibiting user mobility and independence. While the piezoelectric materials integrated shoes have been considered as wearable energy harvesting devices for a long time, they can lose their energy harvesting performance after being used several times due to their brittleness. In this study, we focused on Fe–Co magnetostrictive materials and fabricated Fe–Co magnetostrictive fiber integrated shoes. We revealed that Fe–Co magnetostrictive fiber integrated shoes are capable of generating 1.2 µJ from 1000 steps of usual walking by the Villari (inverse magnetostrictive) effect. It seems that the output energy is dependent on user habit on ambulation, not on their weight. From both a mechanical and functional point of view, Fe–Co magnetostrictive fiber integrated shoes demonstrated stable energy harvesting performance after being used many times. It is likely that Fe–Co magnetostrictive fiber integrated shoes are available as sustainable and wearable energy harvesting devices.

Small-Scale Wind Energy Harvesting From Flow-Induced Vibrations

2011 ◽  
Author(s):  
Vishak Sivadas ◽  
Adam M. Wickenheiser
Keyword(s):  
Energy Harvesting ◽  
Wind Energy ◽  
Boundary Layers ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Environmental Parameters ◽  
Small Scale ◽  
Low Speed ◽  
Structural Deformations ◽  
Flow Induced Vibrations

Significant wind energy exists in the boundary layers around naturally occurring and manmade structures. This energy source has remained largely untapped, even though it presents a significant source of energy for powering wireless devices in built-up areas. This paper discusses a study on harnessing energy from piezoelectric transducers by using bluff body and vortex-induced vibration phenomena induced by low-speed flows. The proposed devices are miniature, scalable, aeroelastic wind harvesters designed for extracting turbulent, low-speed wind energy from the boundary layers around structures. The design configuration consists of a bluff body with a flexible piezoelectric cantilever attached to the trailing edge. In this design, transverse vibrations are induced in the piezoelectric members by alternating vortex shedding. The multi-physics software package COMSOL is used for coupled simulation of the fluid and structural domains, and Matlab is used to couple the structural deformations to the attached power harvesting circuitry. The design and environmental parameters are varied to optimize the configuration and to identify the significant parameters in the design. The lock-in phenomenon, in which the vortex shedding frequency is entrained to the fundamental structural frequency, is exploited to achieve resonance over a range of flow velocities, thus increasing the velocity “bandwidth” of the devices. Simulations are run for different characteristic dimensions or shapes for the bluff body to study the strength and nature of vortex shedding in the presence of vibrating beam sections. The results of parameter variation for the design configuration is presented and discussed with regard to broadband wind energy harvesting.

Review—Bluff Body Flows Applicable to Vehicle Aerodynamics

1980 ◽  
Vol 102 (3) ◽  
pp. 265-274 ◽  
Author(s):  
P. W. Bearman
Keyword(s):  
Bluff Body ◽  
Main Flow ◽  
Wind Tunnels ◽  
Prediction Methods ◽  
Bluff Bodies ◽  
Turbulence Level ◽  
Vehicle Aerodynamics ◽  
Body Shapes ◽  
Bluff Body Flows ◽  
Relative Wind

This paper attempts to review those aspects of bluff body aerodynamics that are relevant to the understanding of vehicle flows. Vehicles often have complex body shapes and are influenced by the proximity of the ground. The effect of the ground is discussed in some detail and results for bluff bodies mounted in wind tunnels above fixed and moving ground planes are presented. It is concluded that drag is little affected by ground proximity and ground representation whereas lift is often sensitive to both. The effect of slanting the base of a bluff body is discussed and the two main flow regimes that result are described. The influence of the wind on vehicle flows is investigated and it is found that vehicle mean flows are sensitive to the turbulence level in the relative wind. Finally numerical prediction methods are considered.

Optimum power of a nonlinear piezomagnetoelastic energy harvester with using multidisciplinary optimization algorithms

2020 ◽  
pp. 1045389X2097443
Author(s):  
Mohammad Tahmasbi ◽  
Asghar Jamshiddoust ◽  
Amin Farrokhabadi
Keyword(s):  
Genetic Algorithm ◽  
Simulated Annealing ◽  
Energy Harvesting ◽  
Energy Harvester ◽  
Random Search ◽  
Electrical Power ◽  
Multidisciplinary Optimization ◽  
Physical Parameters ◽  
Parallel Configuration ◽  
Energy Harvesting Devices

Energy-harvesting devices have been widely used to generate electrical power. Through the use of energy harvesting techniques, ambient vibration energy can be captured and converted into usable electricity in order to create self-powering systems. In the present study, to further improve the efficiency of energy-harvesting devices, a nonlinear piezomagnetoelastic energy harvester is proposed in two different configurations that is parallel and series. In order to optimize the generated electrical power, the physical parameters of the harvester are chosen as the design variables. Classical and Metaheuristic algorithms, namely, random search, genetic algorithm, and simulated annealing are applied to optimize the output power regarding the stress and displacement constraints and feasible variable bounds. Finally, the results of the applied algorithms are compared together. The results demonstrate that most of the implemented algorithms converge to the similar objective function value. The constrained random search methods with SQP and active set algorithms converge faster with small iterations. However, the genetic algorithm and simulated annealing algorithm are more capable to find the global optimum. The obtained results revealed that, before the optimization, the average extracted power in specified time was 3.121 W in parallel configuration and 3.156 W in serial configuration. By using the optimization approaches, the power converged to 4.273 W in parallel configuration and 4.296 W in serial configuration that means the power is increased by 36.9% and 36.1% approximately.

Interaction and acoustics of separated flows from a D-shaped bluff body

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Guangyuan Huang ◽  
Ka Him Seid ◽  
Zhigang Yang ◽  
Randolph Chi Kin Leung
Keyword(s):  
Vortex Shedding ◽  
Bluff Body ◽  
Leading Edge ◽  
Separated Flows ◽  
Pressure Waves ◽  
Bluff Bodies ◽  
Trailing Edge ◽  
Content Type ◽  
Trailing Edges ◽  
Edge Vortex

Purpose For flow around elongated bluff bodies, flow separations would occur over both leading and trailing edges. Interactions between these two separations can be established through acoustic perturbation. In this paper, the flow and the acoustic fields of a D-shaped bluff body (length-to-height ratio L/H = 3.64) are investigated at height-based Reynolds number Re = 23,000 by experimental and numerical methods. The purpose of this paper is to study the acoustic feedback in the interaction of these two separated flows. Design/methodology/approach The flow field is measured by particle image velocimetry, hotwire velocimetry and surface oil flow visualization. The acoustic field is modeled in two dimensions by direct aeroacoustic simulation, which solves the compressible Navier–Stokes equations. The simulation is validated against the experimental results. Findings Separations occur at both the leading and the trailing edges. The leading-edge separation point and the reattaching flow oscillate in accordance with the trailing-edge vortex shedding. Significant pressure waves are generated at the trailing edge by the vortex shedding rather than the leading-edge vortices. Pressure-based cross-correlation analysis is conducted to clarify the effect of the pressure waves on the leading-edge flow structures. Practical implications The understanding of interactions of separated flows over elongated bluff bodies helps to predict aerodynamic drag, structural vibration and noise in engineering applications, such as the aerodynamics of buildings, bridges and road vehicles. Originality/value This paper clarifies the influence of acoustic perturbations in the interaction of separated flows over a D-shaped bluff body. The contribution of the leading- and the trailing-edge vortex in generating acoustic perturbations is investigated as well.

scholarly journals Emerging Devices Based on Two-Dimensional Monolayer Materials for Energy Harvesting

Research ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Feng Ru Fan ◽  
Wenzhuo Wu
Keyword(s):  
Energy Harvesting ◽  
Electrical Power ◽  
Thin Body ◽  
Mechanical And Thermal Properties ◽  
Two Dimensional ◽  
Energy Needs ◽  
Challenges And Opportunities ◽  
Self Powered ◽  
Hybrid Devices ◽  
Energy Harvesting Devices

Two-dimensional (2-D) materials of atomic thickness have attracted considerable interest due to their excellent electrical, optoelectronic, mechanical, and thermal properties, which make them attractive for electronic devices, sensors, and energy systems. Scavenging the otherwise wasted energy from the ambient environment into electrical power holds promise to address the emerging energy needs, in particular for the portable and wearable devices. The versatile properties of 2-D materials together with their atomically thin body create diverse possibilities for the conversion of ambient energy. The present review focuses on the recent key advances in emerging energy-harvesting devices based on monolayer 2-D materials through various mechanisms such as photovoltaic, thermoelectric, piezoelectric, triboelectric, and hydrovoltaic devices, as well as progress for harvesting the osmotic pressure and Wi-Fi wireless energy. The representative achievements regarding the monolayer heterostructures and hybrid devices are also discussed. Finally, we provide a discussion of the challenges and opportunities for 2-D monolayer material-based energy-harvesting devices in the development of self-powered electronics and wearable technologies.

Generalized Airloads Prediction for Bluff Bodies Transported as Slung Loads

2015 ◽  
Author(s):  
Nicholas Motahari ◽  
Nandeesh Hiremath ◽  
Dhwanil Shukla ◽  
Brandon Liberi ◽  
Nikolaus Thorell ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Bluff Body ◽  
Flight Speed ◽  
Navier Stokes ◽  
Bluff Bodies ◽  
Aerodynamic Loads ◽  
Rotation Method ◽  
Continuous Rotation ◽  
Speed Prediction ◽  
Body Shapes

Objects of arbitrary shapes have to be carried as slung loads under aircraft, particularly rotorcraft. The flight speed is limited by the possibility of slung loads going into divergent oscillations. In 2014 we presented a testing-based approach to predict the safe flight speed, applicable to bluff bodies of arbitrary shape. Since then, an extensive variety of bluff-body shapes has been tested, and we venture further towards generalized airload prediction, required for generalized divergence speed prediction. Extending recent work, the Continuous Rotation method is applied to obtain aerodynamic loads on generic shapes: a circular cylinder and a rectangular prism, both with aspect ratio varied systematically. The genesis of the side force on the yawed cylinder, and the differences between rough and smooth cylinders, have been derived from comparisons between experiments and diagnostic computations with an unsteady Navier-Stokes solver. Interpolating Fourier coefficients of the azimuthal load variation appears to be viable to generalize loads on cylinders of varying aspect ratio for both the generic shapes.

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