scholarly journals Numerical Study on Aerodynamic Performance of Different Forms of Adaptive Blades for Vertical Axis Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 880
Author(s):  
Longfeng Hou ◽  
Sheng Shen ◽  
Ying Wang
Keyword(s):  
Young’S Modulus ◽  
Angle Of Attack ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Chord Length ◽  
Vortex Generation ◽  
Active Deformation ◽  
Maximum Deformation ◽  
Deformation Amplitude ◽  
Aerodynamic Performances

The wind energy exploitation technique has been developed very quickly in recent years. The vertical axis wind turbine is a hot research domain due to several advantages: low noise, flexible for installation, ease of maintenance, great safety and credibility, etc. The aerodynamic performances of different forms of airfoils including an active deformation airfoil and a fluid-solid coupling passive airfoil with two-dimensional (2D) and three-dimensional (3D) cases have been investigated numerically in this paper. Firstly, the aerodynamic performances of the airfoils with the maximum deformation amplitudes of their cambers which are 3%, 5% and 7% of the chord length have been discussed, respectively, with the angles of attack in the range of 0° and 20°. Secondly, for the angle of attack set at 18°, the two-way fluid-solid coupling simulations with the Young’s Modulus of 1 Mpa and 2 Mpa have also been investigated. Results show that: (1) for the pseudo 3D and real 3D single active deformation airfoil cases, the lift coefficients increase as the maximum deformation amplitudes augment from 3% to 7% of the chord length at the same angle of attack. With the same maximum deformation amplitude, when the angles of attack increase from 0° to 20°, the lift coefficients which increase firstly and then decrease are bigger than that of the original NACA0012 airfoil. When the maximum deformation amplitude of the pseudo 3D airfoil reaches 5% of the chord length, a relatively good aerodynamic performance with better inhibition effect of vortex generation can be obtained. The 3D vortex distribution demonstrates that the deformable airfoil has a better vortex generation controlling effect at the middle cross-section along the spanwise direction than the non-deformable airfoil. (2) From the aspect of fluid-solid coupling, the lift increases and the drag decreases so that the lift to drag ratio has a big improvement when the Young’s Modulus is equal to 1 Mpa and 2 Mpa. The deformable airfoil can inhibit the generation and the shedding of the surface vortex when the fluid-solid coupling effect is considered.

scholarly journals Numerical Simulation of Unsteady Aerodynamic Performance of Novel Adaptive Airfoil for Vertical Axis Wind Turbine

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4106 ◽  
Author(s):  
Hui Tong ◽  
Jian Fang ◽  
Jinyang Guo ◽  
Kun Lin ◽  
Ying Wang
Keyword(s):  
Wind Turbine ◽  
Control Method ◽  
Active Flow Control ◽  
Great Influence ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Vertical Axis Wind Turbine ◽  
Active Deformation ◽  
Deformation Amplitude ◽  
Deformation Frequency

The aerodynamic performance of the blade determines the power and load characteristics of a wind turbine. In this paper, numerical research of the active deformation of an airfoil with equal thickness camber line was carried out, which shows the great potential of this active flow control method to improve the flow field. The NACA0012 is taken as the reference airfoil, and the inflow wind speed is 9 m/s, the chord length of the airfoil is 0.4 m, and the Reynolds number is 2.5 × 105. The influence factors, such as deformation amplitude and deformation frequency on the aerodynamic performance, were studied at different attack angles before and after stall. Studies have shown that: firstly, at different angles of attack, different deformation amplitudes and frequencies have great influence on the aerodynamic performance of the active deformed airfoil. The active deformation can improve the aerodynamic performance of the airfoil in different degrees in deep stall and light stall regions. Secondly, a suitable deformation amplitude and deformation frequency can improve the aerodynamic performance of airfoil stably and effectively in light stall, which occurs when the deformation amplitude equals to 0.02c and the deformation frequency is lower than 2 Hz, and the maximum lift-drag ratio can be increased by about 25%. Before stall, when the deformation frequency is 2 Hz and amplitude is 0.10c, the airfoil will have a negative drag coefficient in the process of deformation, and the airfoil will produce a thrust which is similar to the energy capture of the flapping foil. This is an unexpected discovery in our research.

The Aerodynamic Performance of Offshore Twin Vertical Axis Wind Turbines With Deflector

2019 ◽  
Author(s):  
Yichen Jiang ◽  
Peidong Zhao ◽  
Li Zou ◽  
Guiyong Zhang ◽  
Zhi Zong
Keyword(s):  
Wind Turbines ◽  
Dynamic Method ◽  
Fluid Dynamic ◽  
Angle Of Attack ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Vertical Axis Wind Turbines ◽  
Simulation Results ◽  
Novel Design ◽  
Local Angle

Abstract A novel design of offshore twin counter-rotating vertical axis wind turbines (VAWTs) with deflector is proposed in this paper. We investigate the performance of the twin VAWTs by the two-dimensional computational fluid dynamic method with the Spalart-Allmaras turbulence model. Then, the performances of twin VAWTs with three kinds of deflectors are compared. The results show that installing the front deflector leads to significant improved aerodynamic performance. To better understand the simulation results, we introduce a simple and effective method to obtain the blade’s angle of attack. The mechanism of enhanced performance by deflector is pointed out, based on the information of the blade’s local angle of attack and flow field. Finally, a guideline on the design of deflector for the twin vertical axis wind turbines is provided.

STUDY ON AERODYNAMIC PERFORMANCE OF THE BIONIC AIRFOIL BASED ON THE SWALLOW'S WING

2013 ◽  
Vol 13 (06) ◽  
pp. 1340022 ◽  
Author(s):  
WEIJUN TIAN ◽  
FANGYUAN LIU ◽  
QIAN CONG ◽  
YURONG LIU ◽  
LUQUAN REN
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Performance ◽  
Wind Tunnel Tests ◽  
Small Wind Turbines ◽  
Aerodynamic Performances ◽  
Drag Ratio ◽  
Bionic Airfoil

This paper demonstrates the design of the airfoil of small wind turbines, the bionic airfoil was inspired by the morphology of the swallow's extended wing. The wind tunnel tests on the bionic and standard airfoils NACA4412 were conducted, and the aerodynamic performances of the airfoils were numerically investigated. The results show that the bionic airfoil has better aerodynamic performance, the lift coefficient and lift-drag ratio are larger than those of the NACA4412; with the angle of attack increases, both the bionic and standard airfoils stall, but the stall characteristics of the bionic airfoil are better.

scholarly journals Numerical Investigation of Aerodynamic Characteristics of NACA 4312 Airfoil with Gurney Flap

2021 ◽  
pp. 1-8
Author(s):  
Subah Mubassira ◽  
Farhana Islam Muna ◽  
Mohammad Ilias Inam
Keyword(s):  
Flow Separation ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Reynold Number ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Chord Length ◽  
Ansys Fluent ◽  
Gurney Flap ◽  
Sst Model

This paper presents a two-dimensional Computational Fluid Dynamics (CFD) analysis on the effect of gurney flap on a NACA 4312 airfoil in a subsonic flow. These numerical simulations were conducted for flap heights 1.5%, 1.75%, 2% and 3% of chord length at fixed Reynold Number, Re (5×105) for different angle of attack (0o ~16o). ANSYS Fluent commercial software was used to conduct these simulations. The flow was considered as incompressible and K-omega Shear Stress Transport (SST) model was selected. The numerical results demonstrate that lift coefficient increase up to around 12o AoA (angle of attack) for NACA 4312 with and without gurney flap. For every AoA lift coefficient and drag coefficient presented proportionate behavior with flap height. However, lift co-efficient was decreased after around  angle of attack due to flow separation. Maximum lift to drag ratio was found at around 4o AoA for every flap length and airfoil with flap of 1.5%C (chord length) had shown the most optimized aerodynamic performance through the analysis. This study concluded that airfoil with gurney flap displayed enhanced aerodynamic performance than the airfoil without gurney flap due to the delay in flow separation.

scholarly journals Aerodynamic Performance Analysis of a Modified Joukowsky Airfoil: Parametric Control of Trailing Edge Thickness

2021 ◽  
Vol 11 (18) ◽  
pp. 8395 ◽  
Author(s):  
Pan Xiong ◽  
Lin Wu ◽  
Xinyuan Chen ◽  
Yingguang Wu ◽  
Wenjun Yang
Keyword(s):  
Vortex Structure ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Performance ◽  
Vortex Generation ◽  
Trailing Edge ◽  
K Value ◽  
Blunt Trailing Edge ◽  
The Impact ◽  
Drag Ratio

In order to ensure the blade strength of large-scale wind turbine, the blunt trailing edge airfoil structure is proposed, aiming at assessing the impact of the trailing edge shape on the flow characteristics and airfoil performance. In this paper, a Joukowsky airfoil is modified by adding the tail thickness parameter K to achieve the purpose of accurately modifying the thickness of the blunt tail edge of the airfoil. Using Ansys Fluent as a tool, a large eddy simulation (LES) model was used to analyze the vortex structure of the airfoil trailing edge. The attack angles were used as variables to analyze the aerodynamic performance of airfoils with different K-values. It was found that when α = 0°, α = 4°, and α = 8°, the lift coefficient and lift–drag ratio increased with increasing K-value. With the increase in the angle of attack from 8° to 12°, the lift–drag ratio of the airfoil with the blunt tail increased from +70% to −7.3% compared with the original airfoil, which shows that the airfoil with the blunt trailing edge has a better aerodynamic performance at a small angle of attack. The aerodynamic characteristics of the airfoil are affected by the periodic shedding of the wake vortex and also have periodic characteristics. By analyzing the vortex structure at the trailing edge, it was found that the value of K can affect the size of the vortex and the position of vortex generation/shedding. When α = 0°, α = 4°, and α = 8°, the blunt trailing edge could improve the aerodynamic performance of the airfoil; when α = 12°, the position of vortex generation changed, which reduced the aerodynamic performance of the airfoil. Therefore, when designing the trailing edge of an airfoil, the thickness of the trailing edge can be designed according to the specific working conditions. It can provide valuable information for the design and optimization of blunt trailing edge airfoil.

scholarly journals Leading Edge Blowing to Mimic and Enhance the Serration Effects for Aerofoil

2021 ◽  
Vol 11 (6) ◽  
pp. 2593
Author(s):  
Yasir Al-Okbi ◽  
Tze Pei Chong ◽  
Oksana Stalnov
Keyword(s):  
Boundary Layer ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Boundary Layer Separation ◽  
Shear Instability ◽  
Vortical Flow ◽  
High Angle ◽  
High Angle Of Attack ◽  
Layer Separation ◽  
Aerodynamic Performances

Leading edge serration is now a well-established and effective passive control device for the reduction of turbulence–leading edge interaction noise, and for the suppression of boundary layer separation at high angle of attack. It is envisaged that leading edge blowing could produce the same mechanisms as those produced by a serrated leading edge to enhance the aeroacoustics and aerodynamic performances of aerofoil. Aeroacoustically, injection of mass airflow from the leading edge (against the incoming turbulent flow) can be an effective mechanism to decrease the turbulence intensity, and/or alter the stagnation point. According to classical theory on the aerofoil leading edge noise, there is a potential for the leading edge blowing to reduce the level of turbulence–leading edge interaction noise radiation. Aerodynamically, after the mixing between the injected air and the incoming flow, a shear instability is likely to be triggered owing to the different flow directions. The resulting vortical flow will then propagate along the main flow direction across the aerofoil surface. These vortical flows generated indirectly owing to the leading edge blowing could also be effective to mitigate boundary layer separation at high angle of attack. The objectives of this paper are to validate these hypotheses, and combine the serration and blowing together on the leading edge to harvest further improvement on the aeroacoustics and aerodynamic performances. Results presented in this paper strongly indicate that leading edge blowing, which is an active flow control method, can indeed mimic and even enhance the bio-inspired leading edge serration effectively.

Numerical Research on the Characteristics of Lift-Drag Type Vertical Axis Wind Turbine

2012 ◽  
Vol 189 ◽  
pp. 448-452
Author(s):  
Yan Jun Chen ◽  
Guo Qing Wu ◽  
Yang Cao ◽  
Dian Gui Huang ◽  
Qin Wang ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Chord Length ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Tip Speed Ratio ◽  
Middle Range ◽  
Parabolic Form ◽  
Cfd Method

Numerical studies are conducted to research the performance of a kind of lift-drag type vertical axis wind turbine (VAWT) affected by solidity with the CFD method. Moving mesh technique is used to construct the model. The Spalart-Allmaras one equation turbulent model and the implicit coupled algorithm based on pressure are selected to solve the transient equations. In this research, how the tip speed ratio and the solidity of blade affect the power coefficient (Cp) of the small H-VAWT is analyzed. The results indicate that Cp curves exhibit approximate parabolic form with its maximum in the middle range of tip speed ratio. The two-blade wind turbine has the lowest Cp while the three-blade one is more powerful and the four-blade one brings the highest power. With the certain number of blades, there is a best chord length, and too long or too short chord length may reduce the Cp.

scholarly journals Numerical simulation of flapping airfoil with alula

2020 ◽  
Vol 12 ◽  
pp. 175682932097798
Author(s):  
Han Bao ◽  
Wenqing Yang ◽  
Dongfu Ma ◽  
Wenping Song ◽  
Bifeng Song
Keyword(s):  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Geometric Parameters ◽  
Flight Performance ◽  
Relative Angle ◽  
Vertical Distance ◽  
Unsteady Effect ◽  
Flapping Airfoil

Bionic micro aerial vehicles have become popular because of their high thrust efficiency and deceptive appearances. Leading edge or trailing edge devices (such as slots or flaps) are often used to improve the flight performance. Birds in nature also have leading-edge devices, known as the alula that can improve their flight performance at large angles of attack. In the present study, the aerodynamic performance of a flapping airfoil with alula is numerically simulated to illustrate the effects of different alula geometric parameters. Different alula relative angles of attack β (the angle between the chord line of the alula and that of the main airfoil) and vertical distances h between the alula and the main airfoil are simulated at pre-stall and post-stall conditions. Results show that at pre-stall condition, the lift increases with the relative angle of attack and the vertical distance, but the aerodynamic performance is degraded in the presence of alula compared with no alula, whereas at post-stall condition, the alula greatly enhances the lift. However, there seems to be an optimal relative angle of attack for the maximum lift enhancement at a fixed vertical distance considering the unsteady effect, which may indicate birds can adjust the alula twisting at different spanwise positions to achieve the best flight performance. Different alula geometric parameters may affect the aerodynamic force by modifying the pressure distribution along the airfoil. The results are instructive for design of flapping-wing bionic unmanned air vehicles.

Experimental Determination of Steady and Unsteady Loads on a Surface Piercing, Ventilated Hydrofoil

1969 ◽  
Vol 13 (01) ◽  
pp. 1-11
Author(s):  
G. E. Ransleben
Keyword(s):  
Rigid Body ◽  
Experimental Determination ◽  
Cross Section ◽  
Angle Of Attack ◽  
Chord Length ◽  
Body Rolling

Measured steady and unsteady section lift and moment coefficients at two spanwise locations on a surface-piercing ventilated hydrofoil are presented. The foil, of wedge cross section, was supported vertically, and submerged one chord length from the tip. Excitation in rigid-body rolling and pitching modes to the cantilevered foil produced the unsteady loads. All tests were made at a nominal angle of attack of 12 deg.

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