Numerical Investigation of Flow past a Wavy Airfoil

2011 ◽  
Vol 110-116 ◽  
pp. 4269-4275
Author(s):  
K. Lam ◽  
Y.F. Lin ◽  
Y. Liu ◽  
L. Zou
Keyword(s):  
Numerical Investigation ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Large Eddy Simulations ◽  
Wavy Surface ◽  
Naca0012 Airfoil ◽  
Large Eddy ◽  
Stall Angle ◽  
Coefficient Reduction

The effect of the wavy surface on the aerodynamic characteristics of an airfoil is studied using the large eddy simulations. A more gentle lift characteristic is obtained during stall. For angles of attack less than the baseline stall angle of a NACA0012 airfoil, a lift coefficient reduction was observed for the wavy airfoils, while the lift coefficient increases up to 23% greater than that of a NACA0012 airfoil when the angle of attack is larger than the baseline stall angle of the NACA0012 airfoil.

scholarly journals The Influence of Boundary Layer Caused by Riblets on the Aircraft Surface

2020 ◽  
Vol 10 (11) ◽  
pp. 3686
Author(s):  
Hongqing Lv ◽  
Zhenqing Wang ◽  
Jiahao Chen ◽  
Lei Xu
Keyword(s):  
Boundary Layer ◽  
Drag Reduction ◽  
Flow Direction ◽  
Angle Of Attack ◽  
Suction Side ◽  
Aerodynamic Characteristics ◽  
Wall Surface ◽  
Friction Resistance ◽  
Naca0012 Airfoil ◽  
Stall Angle

Drag reduction of riblets is one of the most important problems in drag reduction of non-smooth surfaces. In the past two decades, the use of riblets arranged along the flow direction to reduce frictional resistance has received considerable attention. In this paper, we study the plates with the triangular concave grooves, triangular protrusion riblets, trapezoidal concave grooves, trapezoidal protrusion riblets, and circular concave grooves. The numerical simulation method is used to calculate five kinds of plates with grooves and riblets under multiple working conditions. The results showed that the plates with grooves and riblets generated vortices inside the grooves, which separated the incoming flow from the wall surface, and by increasing the thickness of the boundary layer, greatly reducing the average velocity gradient of the wall surface, compared with the smooth flat plate, the friction resistance is reduced. But, lateral riblets and grooves cause additional pressure resistance, which is one order of magnitude higher than the friction resistance. Then, the triangular concave grooves are arranged on the suction and pressure sides of the NACA0012 airfoil, respectively. We calculated the aerodynamic parameters of the both airfoils, and the standard NACA0012 airfoil from the −8° attack angle to their respective stall attack angles. The results showed that the NACA0012 airfoil with triangular concave grooves on the suction side reduced the aerodynamic characteristics of the standard NACA0012 at a small angle of attack, but the stall angle of attack of the standard NACA0012 airfoil was improved, because the grooves ensure that some gas can flow normally on the suction side and delay the separation of the boundary layer. The NACA0012 airfoil with triangular concave grooves on the pressure side did not effectively improve the aerodynamic characteristics: lift–drag ratio decreased and stall angle of attack decreased, but it can increase the lift slightly.

scholarly journals Aerodynamic characteristics of a square cylinder with corner fins

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Qiulei Wang ◽  
Qi Jiang ◽  
Gang Hu ◽  
Xiao Chen ◽  
Chao Li ◽  
...  
Keyword(s):  
Vortex Shedding ◽  
Opposite Effect ◽  
Lift Coefficient ◽  
Underlying Mechanism ◽  
Aerodynamic Characteristics ◽  
Large Eddy Simulations ◽  
Square Cylinder ◽  
Remarkable Effect ◽  
Large Eddy ◽  
Wind Induced Vibration

AbstractThis paper investigates the effect of fitting fins at the corners of a square cylinder on aerodynamic characteristics of the cylinder via wind tunnel tests and large eddy simulations (LES). Although it has been recognized that the corner fins have a remarkable effect on aerodynamic characteristics of a square cylinder, no study has been carried out to systematically evaluate this effect and reveal the underlying mechanism. Three types of corner fin configurations, i.e. fins fitted only to the leading corners, fins fitted only to the trailing corners, and fins fitted to both leading and trailing corners were studied. It was found that the corner fins significantly influence aerodynamic characteristics, such as mean drag coefficient, fluctuating lift coefficient, and vortex shedding of the cylinder. The influences of these corner fin configurations are very different. In general, the leading and trailing fins have an opposite effect on these characteristics. The mechanisms underlying these effects were clarified based on the flow regime visualized via LES. The interesting findings have practical significances not only for reducing aerodynamic forces and wind-induced vibration of infrastructures, but also for enhancing wind-induced vibration-based energy harvesting.

scholarly journals Investigation of a NACA0012 Finite Wing Aerodynamics at Low Reynold’s Numbers and 0º to 90º Angle of Attack

2019 ◽  
Author(s):  
Shahrooz Eftekhari ◽  
Abdulkareem Shafiq Mahdi Al-Obaidi
Keyword(s):  
Drag Force ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Poor Performance ◽  
Aerodynamic Characteristics ◽  
Airfoil Surface ◽  
Wing Geometry ◽  
Stall Angle ◽  
Finite Wing ◽  
Lift And Drag

The aerodynamic characteristics of a NACA0012 wing geometry at low Reynold’s numbers and angle of attack ranging from 0º to 90º are investigated using numerical simulations and the results are validated by wind tunnel experiments. Further experiments are conducted at low Reynold’s numbers of 1 × 105, 2 × 105 and 3 × 105. Findings of the study show a similar trend for the lift and drag coefficients at all the investigated Reynold’s numbers. The lift coefficient is linearly increased with angle of attack until it reaches its maximum value at 32º which is the stall angle. It is observed that further increment in angle of attack results in decrement of lift coefficient until it reaches its minimum value at 90º angle of attack. The drag force acting on the airfoil increases as the angle of attack is increased and increment in the drag force results in change of laminar flow to turbulent flow. As the turbulence gets higher the flow starts to separate from the airfoil surface due to eddies generated by turbulence. Hence, the lift force generated by the wing is reduced and drag force is increased simultaneously, which results in poor performance of the wing.

Numerical Study on Aerodynamic Characteristics of NACA0015

2013 ◽  
Vol 302 ◽  
pp. 640-645
Author(s):  
Su Jeong Lee ◽  
Eui Chul Jeong ◽  
Hee Chang Lim
Keyword(s):  
Pressure Distribution ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Vertical Axis ◽  
Aerodynamic Characteristics ◽  
Surface Pressure Distribution ◽  
Maximum Value ◽  
Stall Angle ◽  
Near Wall

In this study, a numerical simulation is made to understand the effect of the angle of attack on a NACA airfoil, which will be used for a basic shape to apply for making the vertical axis Darius wind turbine. The near-wall y+ value which is less than 1 is known to be most desirable for a near-wall modeling. Therefore, this study is aiming to observe the variation and find the optimized value of y+. The Reynolds number used in this study was 360,000, where the chord length and the velocity were 0.12m and 43.8m/s, respectively. Generally, the lift coefficient of the airfoil tends to increase as the angle of attack increases and it decreases substantially at the stall angle and then it decreases. As expected, the lift coefficient increases rapidly from 0 to 10° and then after the sudden drop of the lift (i.e., the stall) at around 10 to 16° depending on the y+ value. In this paper, it seems to be reliable and appropriate to use y+ value close to 1. From the surface pressure distribution, from the result obtained the ratio of pressure distribution of maximum value to the minimum value was 1.89and these peaks move forward to backward as the angle of attack increases.

scholarly journals Hydrodynamics of gliding penguin flipper suggests the adjustment of sweepback with swimming speeds

2021 ◽  
Author(s):  
Masateru Maeda ◽  
Natsuki Harada ◽  
Hiroto Tanaka
Keyword(s):  
Large Eddy Simulation ◽  
Cfd Simulation ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Force Balance ◽  
Hydrodynamic Performance ◽  
Vertical Force ◽  
Sweep Angle ◽  
Eddy Simulation ◽  
Large Eddy

Hydrodynamic performance of a gliding penguin flipper (wing) considering the backward sweep was estimated with computational fluid dynamics (CFD) simulation. A flipper of a gentoo penguin (Pygoscelis papua) was 3D scanned, smoothed, and a numerical fluid mesh was generated. For accurate yet resource-saving computation, an embedded large-eddy simulation (ELES) methods was employed, where the flow near the flipper was solved with large-eddy simulation (LES) and flow far away from the flipper was solved with Reynolds-averaged Navier-Stokes (RANS). The relative flow speed was fixed at 2 m s-1, close to the typical foraging speed for the penguin species. The sweep angle was set to be 0°, 30°, and 60°, while the angle of attack was varied between -40° and 40°, both are within the realistic ranges in the wing kinematics measurement of penguins in an aquarium. It was revealed that a higher sweep angle reduces the lift slope, but the lift coefficient is unchanged at a high angle of attack. Drag coefficient was reduced across the angles of attack with increasing the sweep angles. The drag polars suggest the sweep angle may be adjusted with the change in swimming speed and anhedral (negative dihedral) angle to minimise drag while maintaining the vertical force balance to counteract the positive buoyancy. This will effectively expand the swimming envelope of the gliding penguin, similar to a flying counterpart such as swift.

scholarly journals Experimental Investigation of Lift Enhancement and Drag Reduction of Discrete Co-Flow Jet Rotor Airfoil

2021 ◽  
Vol 11 (20) ◽  
pp. 9561
Author(s):  
Shunlei Zhang ◽  
Xudong Yang ◽  
Bifeng Song ◽  
Zhuoyuan Li ◽  
Bo Wang
Keyword(s):  
Drag Reduction ◽  
High Performance ◽  
Performance Enhancement ◽  
Fundamental Problem ◽  
Unit Length ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Relative Unit ◽  
Lift Enhancement ◽  
Stall Angle

Rotor airfoil design involves multi-point and multi-objective complex constraints. How to significantly improve the maximum lift coefficient and lift-to-drag ratio of rotor airfoil is a fundamental problem, which should be solved urgently in the development of high-performance helicopter rotor blades. To address this, discrete co-flow jet (DCFJ) technology is one methods with the most potential that can be harnessed to improve the performance of the rotor airfoil. In this study, wind tunnel experiments are conducted to study the effect of DCFJ technology on lift enhancement and drag reduction of OA312 airfoil. Furthermore, the performance improvement effects of the open co-flow jet (CFJ) and DCFJ technologies are studied. In addition, the influence of fundamental parameters, such as the obstruction factor and relative unit length, are analyzed. Results demonstrate that DCFJ technology is better than CFJ technology on the performance enhancement of the OA312 airfoil. Moreover, the DCFJ rotor airfoil can significantly reduce the drag coefficient and increase the maximum lift coefficient and the stall angle of attack. The maximum lift coefficient can be increased by nearly 67.3%, and the stall angle of attack can be delayed by about 12°. The DCFJ rotor airfoil can achieve the optimal performance when the obstruction factor is 1/2 and the relative unit length is 0.025.

scholarly journals Aerodynamic and Vibration Characteristics of the Micro-Octocopter at Low Reynolds Number

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Xiaohua Zou ◽  
Mingsheng Ling ◽  
Wenzheng Zhai
Keyword(s):  
Reynolds Number ◽  
Load Capacity ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Vibration Characteristics ◽  
Low Reynolds ◽  
Vibration Performance ◽  
Drag Ratio ◽  
Lift To Drag Ratio

With the development of flight technology, the need for stable aerodynamic and vibration performance of the aircraft in the civil and military fields has gradually increased. In this case, the requirements for aerodynamic and vibration characteristics of the aircraft have also been strengthened. The existing four-rotor aircraft carries limited airborne equipment and payload, while the current eight-rotor aircraft adopts a plane layout. The size of the propeller is generally fixed, including the load capacity. The upper and lower tower layout analyzed in this paper can effectively solve the problems of insufficient four-axis load and unstable aerodynamic and vibration performance of the existing eight-axis aircraft. This paper takes the miniature octorotor as the research object and studies the aerodynamic characteristics of the miniature octorotor at different low Reynolds numbers, different air pressures and thicknesses, and the lift coefficient and lift-to-drag ratio, as well as the vibration under different elastic moduli and air pressure characteristics. The research algorithm adopted in this paper is the numerical method of fluid-solid cohesion and the control equation of flow field analysis. The research results show that, with the increase in the Reynolds number within a certain range, the aerodynamic characteristics of the miniature octorotor gradually become better. When the elastic modulus is 2.5 E, the aircraft’s specific performance is that the lift increases, the critical angle of attack increases, the drag decreases, the lift-to-drag ratio increases significantly, and the angle of attack decreases. However, the transition position of the flow around the airfoil surface is getting closer to the leading edge, and its state is more likely to transition from laminar flow to turbulent flow. When the unidirectional carbon fiber-reinforced thickness is 0.2 mm and the thin arc-shaped airfoil with the convex structure has a uniform thickness of 2.5% and a uniform curvature of 4.5%, the aerodynamic and vibration characteristics of the octorotor aircraft are most beneficial to flight.

scholarly journals Design and Validation of a New Morphing Camber System by Testing in the Price—Païdoussis Subsonic Wind Tunnel

Aerospace ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 23 ◽  
Author(s):  
David Communier ◽  
Ruxandra Mihaela Botez ◽  
Tony Wong
Keyword(s):  
Wind Tunnel ◽  
Unmanned Aerial Vehicle ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Trailing Edge ◽  
Subsonic Wind Tunnel ◽  
Aerial Vehicle ◽  
Stall Angle

This paper presents the design and wind tunnel testing of a morphing camber system and an estimation of performances on an unmanned aerial vehicle. The morphing camber system is a combination of two subsystems: the morphing trailing edge and the morphing leading edge. Results of the present study show that the aerodynamics effects of the two subsystems are combined, without interfering with each other on the wing. The morphing camber system acts only on the lift coefficient at a 0° angle of attack when morphing the trailing edge, and only on the stall angle when morphing the leading edge. The behavior of the aerodynamics performances from the MTE and the MLE should allow individual control of the morphing camber trailing and leading edges. The estimation of the performances of the morphing camber on an unmanned aerial vehicle indicates that the morphing of the camber allows a drag reduction. This result is due to the smaller angle of attack needed for an unmanned aerial vehicle equipped with the morphing camber system than an unmanned aerial vehicle equipped with classical aileron. In the case study, the morphing camber system was found to allow a reduction of the drag when the lift coefficient was higher than 0.48.

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