Numerical study on the power extraction performance of a flapping foil with a flexible tail

2015 ◽  
Vol 27 (1) ◽  
pp. 013602 ◽  
Author(s):  
J. Wu ◽  
C. Shu ◽  
N. Zhao ◽  
F.-B. Tian
Keyword(s):  
Numerical Study ◽  
Flexible Tail ◽  
Power Extraction ◽  
Flapping Foil ◽  
Extraction Performance

Use of synthetic jet to a fully-active flapping foil for power extraction enhancement

2020 ◽  
pp. 095440622091522
Author(s):  
Yadong Li ◽  
Guoqing Zhou ◽  
Jie Wu
Keyword(s):  
Vortex Shedding ◽  
Extraction Efficiency ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Foil Surface ◽  
Power Extraction ◽  
Flapping Foil ◽  
Extraction Performance ◽  
Rotational Motions ◽  
Inclined Angle

The power extraction performance of a fully-active flapping foil with synthetic jet is numerically investigated in this work. An elliptic airfoil with ratio of 8, which is placed in a two-dimensional laminar flow, is adopted to extract power from the flow. The foil implements the imposed translational and rotational motions synchronously. A pair of synthetic jets with the same frequency and strength is integrated into the upper and lower surfaces of flapping foil. As a result, the flow field around the foil could be affected by the synthetic jets greatly. At the Reynolds number of 1000 and the pitching axis location of half chord, the effects of the jet strength, the inclined angle between the jet direction and the chord line, as well as the phase angle between the synthetic jets and the flapping motion on the power extraction performance are systematically investigated. Compared with the traditional flapping foil, it is demonstrated that the enhancement of power extraction efficiency can be achieved with the help of synthetic jets. Based on the numerical analysis, it is indicated that the jet flow on the foil surfaces alters the vortex-shedding process and modifies the pressure distribution on the foil surface. As a result, the overall power extraction of the flapping foil can be benefitted.

scholarly journals Effect of Rotation Friction Ratio on the Power Extraction Performance of a Passive Rotation VAWT

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Jianyang Zhu ◽  
Changbin Tian
Keyword(s):  
Numerical Study ◽  
Large Angle ◽  
Rotation Velocity ◽  
Vertical Axis ◽  
Coupling Model ◽  
Working Environment ◽  
Vertical Axis Wind Turbine ◽  
Power Extraction ◽  
Passive Rotation ◽  
Extraction Performance

This paper performs a systematic numerical study to investigate the effect of rotation friction ratio on the power extraction performance of a passive rotation H-type vertical axis wind turbine (H-VAWT). In contrast to the previous literature, the present work does not impose rotation velocity on the turbine, and the rotation friction ratio which reflects the effect of external load characteristics on the turbine is introduced to the governing equation of the turbine. During each iteration, the rotation velocity of the turbine is computed after having determined the aerodynamic torque exerted on the blade of the turbine. This is more consistent with the actual working environment of the H-VAWT. A novel numerical coupling model was developed to simulate the interaction between the fluid and the passive rotation of the H-VAWT; then, the power extraction performance of the turbine with different rotation friction ratio was systematically analyzed. The results demonstrate that the power extraction performance of H-VAWT will be enhanced when the H-VAWT has appropriate rotation friction ratio. It is also found that the flow separation induced by large angle of attack is alleviated essentially if the H-VAWT has appropriate rotation friction ratio, which makes the H-VAWT have better energy extraction performance.

Influence of stroke deviation on the power extraction performance of a fully-active flapping foil

2016 ◽  
Vol 94 ◽  
pp. 440-451 ◽  
Author(s):  
Jie Wu ◽  
Yongliang Chen ◽  
Ning Zhao ◽  
Tongguang Wang
Keyword(s):  
Power Extraction ◽  
Flapping Foil ◽  
Extraction Performance

Power Extraction Performance of a Semi-activated Flapping Foil in Gusty Flow

2017 ◽  
Vol 14 (1) ◽  
pp. 99-110 ◽  
Author(s):  
Jiapu Zhan ◽  
Bing Xu ◽  
Jie Wu ◽  
Jing Wu
Keyword(s):  
Power Extraction ◽  
Flapping Foil ◽  
Extraction Performance

scholarly journals Numerical Study of an Oscillating-Wing Wingmill for Ocean Current Energy Harvesting: Fluid-Solid-Body Interaction with Feedback Control

2020 ◽  
Vol 9 (1) ◽  
pp. 23
Author(s):  
David Balam-Tamayo ◽  
Carlos Málaga ◽  
Bernardo Figueroa-Espinoza
Keyword(s):  
Energy Harvesting ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Ocean Current ◽  
Control Synthesis ◽  
Dimensionless Number ◽  
Control Law ◽  
Loop Control ◽  
Power Extraction ◽  
Current Energy

The performance and flow around an oscillating foil device for current energy extraction (a wingmill) was studied through numerical simulations. OpenFOAM was used in order to study the two-dimensional (2D) flow around a wingmill. A closed loop control law was coded in order to follow a reference angle of attack. The objective of this control law is to modify the angle of attack in order to enhance the lift force (and increase power extraction). Dimensional analysis suggests a compromise between the generator (or damper) stiffness and actuator/control gains, so a parametric study was carried out while using a new dimensionless number, called B, which represents this compromise. It was found that there is a maximum on the efficiency curve in terms of the aforementioned dimensionless parameter. The lessons that are learned from this fluid-structure and feedback coupling are discussed; this interaction, combined with the feedback dynamics, may trigger dynamic stall, thus decreasing the performance. Moreover, if the control strategy is not carefully selected, then the energy spent on the actuator may affect efficiency considerably. This type of simulation could allow for the system identification, control synthesis, and optimization of energy harvesting devices in future studies.

scholarly journals A Model for Performance Estimation of Flapping Foil Operating as Biomimetic Stream Energy Device

2020 ◽  
Vol 9 (1) ◽  
pp. 21
Author(s):  
Iro E. Malefaki ◽  
Kostas A. Belibassakis
Keyword(s):  
Vertical Axis ◽  
Flow Speed ◽  
Performance Estimation ◽  
Speed Ratio ◽  
Power Extraction ◽  
Flapping Foil ◽  
Flow Energy ◽  
Novel Concept ◽  
Angular Oscillations ◽  
Energy Converters

During the recent period intensive research has focused on the advancement of engineering and technology aspects concerning the development and optimization of wave and current energy converters driven by the need to increase the percentage of marine renewable sources in the energy-production mix, particularly from offshore installations. Most stream energy-harvesting devices are based on hydro-turbines, and their performance is dependent on the ratio of the blade-tip speed to incident-flow speed. As the oncoming speed of natural-occurring currents varies randomly, there is a penalty for the latter device’s performance when operating at non-constant tip-speed ratio away from the design value. Unlike conventional turbines that are characterized by a single degree of freedom rotating around an axis, a novel concept is examined concerning hydrokinetic energy converters based on oscillating hydrofoils. The biomimetic device includes a rotating, vertically mounted, biomimetic wing, supported by an arm linked at a pivot point on the mid-chord. Activated by a controllable self-pitching motion the system performs angular oscillations around the vertical axis in incoming flow. In this work, the performance of the above flapping-foil, biomimetic flow energy harvester is investigated by application of a semi-3D model based on unsteady hydrofoil theory and the results are verified by comparison to experimental data and a 3D boundary element method based on vortex rings. By systematical application of the model the power extraction and efficiency of the system is presented for various cases including different geometric, mechanical, and kinematic parameters, and the optimal performance of the system is determined.

Experimental and Numerical Study on the Flow Field Around a Parallel-Foil Turbine

2020 ◽  
Author(s):  
Yulu Wang ◽  
Di Zhang ◽  
Yonghui Xie
Keyword(s):  
Flow Field ◽  
Aerodynamic Force ◽  
Numerical Study ◽  
Energy Extraction ◽  
Reduced Frequency ◽  
Image Velocimetry ◽  
Efficiency Increase ◽  
Oscillation Process ◽  
Effective Angle ◽  
Extraction Performance

Abstract An experiment facility of parallel-foil turbine is proposed in this study. The flow field around foils at different reduced frequency, pitching amplitude and plunging amplitude is measured by 2D Particle Image Velocimetry (PIV) system. And the energy extraction performance at different motion parameters is analyzed numerically. The comparison between experimental and numerical flow field is conducted at different reduced frequency. The evolution of flow field and the aerodynamic force with different pitching amplitude and plunging amplitude are discussed. The effect of pitching amplitude and plunging amplitude on energy extraction performance is obtained. Results indicate that the pitching amplitude can increase the range and the strength of acceleration area by varying the pitching velocity and the effective angle of attack. The optimal extraction performance appears at 70°. Due to the increase in plunging amplitude, the energy extraction performance and efficiency increase gradually. The optimal plunging amplitude is 1.0. The pitching amplitude and the plunging amplitude influence the power output by affecting the vortex shedding and the flow reattachment in oscillation process.

scholarly journals The Effect of Damping Coefficient, Spring Coefficient, and Mass Ratio on the Power Extraction Performance of a Semiactive Flapping Wing

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Jianyang Zhu
Keyword(s):  
Power Efficiency ◽  
Flapping Wing ◽  
Damping Coefficient ◽  
Numerical Code ◽  
Power Coefficient ◽  
Mass Ratio ◽  
Mean Power ◽  
Power Extraction ◽  
Extraction Performance ◽  
Spring Coefficient

The effect of varying damping coefficient C∗, spring coefficient K∗, and mass ratio M∗ on the semiactive flapping wing power extraction performance was numerically studied in this paper. A numerical code based on Finite Volume method to solve the two-dimensional Navier-Stokes equations and coupled with Finite Center Difference method to solve the passive plunging motion equation is developed. At a Reynolds number of 3400 and the pitching axis at quarter chord from the leading edge of the wing, the power extraction performance of the semiactive flapping wing with different damping coefficient, spring coefficient, and mass ratio is systematically investigated. The optimal set of spring coefficient is found at a value of 1.00. However, the variation of mass ratio M∗ cannot increase the maximum mean power coefficient and power efficiency, but it can influence the value of damping coefficient C∗ at which the wing achieves the maximum mean power coefficient and power efficiency. Moreover, insensitivity of the mean power coefficient and power efficiency to the variation of damping coefficient C∗ is observed for the wing with smaller mass ratio, which indicates the wing with smaller M∗ has better working stability.

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