scholarly journals Numerical Study on the Effect of Non-Sinusoidal Motion on the Energy Extraction Performance of Parallel Foils

2019 ◽  
Vol 9 (3) ◽  
pp. 384
Author(s):  
Yulu Wang ◽  
Fahui Zhu ◽  
Yonghui Xie
Keyword(s):  
Lift Force ◽  
Numerical Study ◽  
Average Power ◽  
Power Coefficient ◽  
Energy Extraction ◽  
Pitching Motion ◽  
Evolution Law ◽  
Sinusoidal Motion ◽  
Oscillation Process ◽  
Extraction Performance

The effect of non-sinusoidal motion which influences the energy extraction performance of foil is considered in this paper. Two oscillation motions, the combined non-sinusoidal plunging and sinusoidal pitching motion, as well as the combined non-sinusoidal pitching and sinusoidal plunging motion, are selected to investigate the oscillation process of two-dimensional parallel foils numerically. The optimal oscillation motion and average power coefficient at different combined motions are gained. The effects of the plunging motion and pitching motion at different oscillation motions are analyzed, and the evolution law of the foil lift force and vortex field are obtained. It is indicated that the non-sinusoidal motion has a significant influence on energy extraction. When the motion is combined (non-sinusoidal plunging and sinusoidal pitching motion), the best extraction performance is gained at Kh = −0.5. The maximal CPm is 0.375 and the maximal η is 0.188. When the motion is combined (non-sinusoidal pitching and sinusoidal plunging motion), the maximal CPm is 0.623 and the maximal η is 0.312 which appear at Kθ = 2. For the same frequency, the more the plunging motion is similar to the sinusoidal motion, the more energy is extracted by foils. While the more the pitching motion approximates to the square wave, the worse the achieved extraction performance is.

Numerical Investigation Into the Energy Extraction Characteristics of Parallel Dual-Foil Turbine

2018 ◽  
Author(s):  
Wei Jiang ◽  
Yulu Wang ◽  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Lift Force ◽  
Ground Effect ◽  
Power Coefficient ◽  
Navier Stokes ◽  
Energy Extraction ◽  
Pitching Motion ◽  
Power Generator ◽  
Higher Power ◽  
Extraction Performance ◽  
Parallel Configuration

A new concept of power generator using two oscillating foils in parallel configuration to extract energy from fluid is proposed and numerically tested in the present study. The theoretical performance of the turbine in this form is investigated through unsteady two-dimensional laminar-flow Navier-Stokes simulations. The effect of the interaction between the two foils is studied at different pitching amplitudes and phase differences between the two foils. The energy extraction performance, instantaneous force coefficients and flow details are compared between single foil and dual foils, and thus the mechanism of performance improvement by wing-in-ground effect is revealed. Two different kinds of asymmetric sinusoidal motions are utilized to further improve the performance of the turbine. Numerical results indicate that anti-phase mode can achieve higher power coefficient than the in-phase mode. The contracted passage under anti-phase mode helps produce larger lift force and power coefficient. The maximum power coefficient per foil for anti-phase dual foils is 1.4% higher than that of single foil. The asymmetric sinusoidal pitching motion in phase can improve the synchronization between plunging velocity and lift force and thus further enhance the energy extraction performance by 1.3%. Besides, the pitching motion with asymmetric amplitude also can increase the power coefficient somehow, but the improvement is very limited.

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.

Flow Energy Harvesting of an Oscillating Foil With Rigid and Passive Surface Flexibility

2017 ◽  
Author(s):  
Alexander D. Totpal ◽  
Firas F. Siala ◽  
James A. Liburdy
Keyword(s):  
Energy Harvesting ◽  
Flow Field ◽  
Parameter Space ◽  
Operating Parameter ◽  
Leading Edge ◽  
Power Coefficient ◽  
Phase Lag ◽  
Energy Extraction ◽  
Force Measurements ◽  
Extraction Performance

The aerodynamic performance of an oscillating pitching and plunging foil operating in the energy harvesting mode is experimentally investigated. Experiments are conducted in a closed-loop recirculating wind tunnel at Re of 24,000 to 48,000, and reduced frequencies (k) of 0.04 to 0.08. Foil kinematics are varied through the following parameter space: heaving amplitude of 0.3c, pitching amplitudes of θ0 = 45° to 75°, as well as phase lag between sinusoidal pitching and heaving motions of Φ = 30° to 120°. Aerodynamic force measurements are collected to show the energy extraction performance (power coefficient and efficiency) of the foil. Coupled with the force measurements, flow fields are collected using particle image velocimetry. The flow field characteristics are used to supplement the force results, shedding light into flow features that contribute to increased energy extraction at these k values. In addition, inertia-induced passive chord-wise flexibility at the leading edge (LE) of the foil is investigated in order to assess its feasibility in this application. Results indicate that favorable performance occurs near θ0 = 45°, Φ = 90° and k = 0.08. When k is decreased (through increased U∞) to 0.04, overall extraction performance becomes insensitive to θ0 and Φ. This is supported by the flow field measurements, which show premature leading edge vortex (LEV) evolution and detachment from the foil surface. Although overall performance was reduced with the passive LE flexibility, these results indicate that a proper tuning of the LE may result in a delay of the LEV detachment time, yielding increased energy harvesting at this otherwise inefficient operating parameter space.

Numerical Investigation of a Vertical Axis Wind Turbine Performance Characterization Using New Variable Pitch Control Scheme

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Amin A. Mohammed ◽  
Ahmet Z. Sahin ◽  
Hassen M. Ouakad
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Numerical Study ◽  
Average Power ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Variable Pitch ◽  
De Algorithm

Abstract A double multiple streamtube model coupled with variable pitch methodology is used to analyze the performance characteristics of a small-scale straight-bladed Darrieus type vertical axis wind turbine (SB-VAWT). The numerical study revealed that a fixed pitch of −2.5 deg could greatly enhance the performance of the wind turbine. However, no improvement is observed in the starting torque capacity. Furthermore, the performance of upwind and downwind zones has been investigated, and it is found that the VAWT starting capacity is improved by increasing/decreasing the pitch angle upwind/downwind of the turbine. To optimize the performance, four cases of variable pitch angle schemes of sinusoidal nature were examined. The parameters of the sinusoidal functions were optimized using differential evolution (DE) algorithm with different cost functions. The results showed improvement in the power coefficient, yet with low starting capacity enhancement. Among the objective functions used in DE algorithm, the negative of the average power coefficient is found to lead to the best starting capacity with moderate peak power coefficient.

Numerical analysis of the effect of the mutual interaction between closely separated variable pitch vertical axis wind turbines

2020 ◽  
pp. 0309524X2097167
Author(s):  
Mohammed Shaheen
Keyword(s):  
Wind Turbines ◽  
Numerical Study ◽  
Average Power ◽  
Mutual Effect ◽  
Vertical Axis ◽  
Mutual Interaction ◽  
Power Coefficient ◽  
Basic Unit ◽  
Variable Pitch ◽  
Vertical Axis Wind Turbines

Recent researches have proven that mutual interaction between vertical axis wind turbines (VAWTs) results in enhancement in the average power coefficient. Efficient VAWT clusters have been created to provide wind farms having higher power densities compared to conventional horizontal vertical axis wind turbine farms. The created clusters adopted fixed pitch VAWTs in studying the mutual interaction in close vicinity. This paper extends the investigation of the mutual effect between variable pitch VAWTs in closely oriented turbine clusters. A numerical study is performed using commercial Fluent ANSYS code in order to study the effect of gap distances, phase shifts, and oblique angles for co-rotating and counter-rotating arrangements of two variable pitch VAWTs. The results showed improvement in the performance of two turbine clusters up to 26% compared to isolated turbines. Three turbine clusters are also tested numerically based on the results of the two turbine clusters. The created three turbine cluster represents a basic unit to construct a more efficient wind farm. The results of the developed three turbine cluster showed an increase in the average power coefficient by 38% higher than that of isolated turbines.

scholarly journals Numerical Analysis of Leading-Edge Vortex Effect on Tidal Current Energy Extraction Performance for Chord-Wise Deformable Oscillating Hydrofoil

2019 ◽  
Vol 7 (11) ◽  
pp. 398
Author(s):  
Xu ◽  
Zhu ◽  
Guan ◽  
Zhan
Keyword(s):  
Surface Pressure ◽  
Pressure Difference ◽  
Lift Force ◽  
Leading Edge ◽  
Energy Extraction ◽  
Tidal Current Energy ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Extraction Performance ◽  
Attached Vortex

To improve the energy extraction performance of the oscillating hydrofoil, the lift force that acts on the oscillating hydrofoil is analyzed. The pressure difference between the oscillating hydrofoil‘s opposing surfaces is dominant to generate the lift force. Forming and shedding of the leading-edge vortex from the hydrofoil surface determines the pressure difference between the opposing surfaces of the oscillating hydrofoil. In this paper, the hydrofoil with different chord flexibility coefficients and maximum offset at the trailing edge are analyzed to obtain the power coefficient, lift coefficient, and moment coefficient of the oscillating hydrofoil. The influence mechanism of chord-wise deformation of the oscillating hydrofoil on the energy extraction performance is explored. According to the Kutta–Joukowsky condition and the Stokes’ theorem, the relationship between the attached vortex on the hydrofoil and the surface pressure of the hydrofoil, the surface pressure difference of the hydrofoil, and the lift force that acts on the hydrofoil are investigated. By quantifying the vortex intensity, the ascending-shedding process of the attached vortex on the hydrofoil is characterized. Finally, the complete influence chain among the chord-wise flexure, the attached vortex on the hydrofoil, and the energy extraction performance of the oscillating hydrofoil is established.

scholarly journals Numerical study into the effects of effective angle of attack motions on energy extraction performance of parallel foils

2018 ◽  
Vol 22 (Suppl. 2) ◽  
pp. 371-381
Author(s):  
Yu-Lu Wang ◽  
Wei Jiang ◽  
Yong-Hui Xie
Keyword(s):  
Working Condition ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Engineering Practice ◽  
Energy Extraction ◽  
Extraction Working ◽  
Effective Angle ◽  
Extraction Processes ◽  
Extraction Performance ◽  
Aerodynamic Lift

The effects of different effective angle of attack motions on flapping foil are considered. Energy extraction characteristics of parallel foils with combined plunging and pitching motions at multiple working conditions are systematically analyzed. The energy extraction processes of dual foil at different effective angle of attack motions and reduced frequencies are simulated, respectively. In the range of parameters discussed in this paper, the increase of Ke improves the energy extraction performance of foil effectively. Every effective angle of attack motion has a frequency which can obtain the optimal extraction performance. The optimal energy extraction working condition is Ke = 2 and k = 0.8, where the extraction efficiency of dual foil achieves 25.8%. The synchronicity of the aerodynamic lift and the plunging motion is increased with increase in Ke. This paper provides a significant reference to the further study and popularization in engineering practice of parallel foils energy extraction.

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