Investigation into Aerodynamic Characteristics and Flow Structures of Rectangular Flat-plate Wings of Very Small Aspect Ratios at All Angle of Attack

ABSTRACTTo realize the relationship between flow structures of wingtip vortices and post stall characteristics of low aspect-ratio wings, this paper experimentally studies the aerodynamic characteristics and the corresponding flow structures of the rectangular thin-plate wings at Reynolds numbers between 104 and 105. The aerodynamic properties to be studied include lift, drag, slopes at linear and nonlinear range of the lift curves and lift-to-drag ratios of the tested wings with the aspect ratio varying from 1.0 to 3.0. The flow structures regarding the leading-edge separation vortices and wingtip vortices at upper surface and near-wake regions of the wings are also investigated by smoke-wire visualization. Results indicate that the high stall angle of attack and vortex lift are clearly manifested to induce the nonlinear increase in the lift curves as the aspect ratio reaches less than 1.6. This phenomenon is specifically observed to augment the aerodynamic properties with the decrease of the aspect ratio. Additionally, the corresponding flow visualization also indicates that the wingtip vortices and the areas of highly affected regions are duly increased with the increase of the angle of attack up to 40°, which makes certain that the extra increase of the nonlinear lift results from these vortices. This result can be practically applied to the planform design for unmanned aerial vehicles.

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Flow past flat plate at angle of attack; numerical studies using S-A, LES and IDDES

51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition ◽

10.2514/6.2013-240 ◽

2013 ◽

Author(s):

Marcel Ilie

Keyword(s):

Flat Plate ◽

Angle Of Attack ◽

Numerical Studies ◽

Flow Past

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Rarefied gas flow past a flat plate at zero angle of attack

Physics of Fluids ◽

10.1063/5.0014629 ◽

2020 ◽

Vol 32 (8) ◽

pp. 087108

Author(s):

A. A. Abramov ◽

A. V. Butkovskii ◽

O. G. Buzykin

Keyword(s):

Flat Plate ◽

Gas Flow ◽

Rarefied Gas ◽

Angle Of Attack ◽

Rarefied Gas Flow ◽

Flow Past

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Oscillatory Natural Convection of a Liquid Metal in Circular Cylinders

Journal of Heat Transfer ◽

10.1115/1.2910915 ◽

1994 ◽

Vol 116 (3) ◽

pp. 627-632 ◽

Cited By ~ 14

Author(s):

Y. Kamotani ◽

F.-B. Weng ◽

S. Ostrach ◽

J. Platt

Keyword(s):

Experimental Study ◽

Natural Convection ◽

Liquid Metal ◽

Oscillatory Flow ◽

Circular Cylinders ◽

Flow Structures ◽

Supercritical Flow ◽

Aspect Ratios ◽

Oscillation Frequencies ◽

Rayleigh Numbers

An experimental study is made of natural convection oscillations in gallium melts enclosed by right circular cylinders with differentially heated end walls. Cases heated from below are examined for angles of inclination (φ) ranging from 0 deg (vertical) to 75 deg with aspect ratios Ar (height/diameter) of 2, 3, and 4. Temperature measurements are made along the circumference of the cylinder to detect the oscillations, from which the oscillatory flow structures are inferred. The critical Rayleigh numbers and oscillation frequencies are determined. For Ar=3 and φ = 0 deg, 30 deg the supercritical flow structures are discussed in detail.

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Optimal Position of Rectangular Vortex Generator for Heat Transfer Enhancement in a Flat-Plate Channel

Volume 1: Aerospace Heat Transfer; Computational Heat Transfer; Education; Environmental Heat Transfer; Fire and Combustion Systems; Gas Turbine Heat Transfer; Heat Transfer in Electronic Equipment; Heat Transfer in Energy Systems ◽

10.1115/ht2017-4904 ◽

2017 ◽

Author(s):

Tariq Amin Khan ◽

Wei Li ◽

Zhengjiang Zhang ◽

Jincai Du ◽

Sadiq Amin Khan ◽

...

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Numerical Simulations ◽

Flat Plate ◽

Heat Transfer Enhancement ◽

Angle Of Attack ◽

Vortex Generator ◽

Transfer Enhancement ◽

Optimal Position ◽

Plate Channel

Heat transfer is a naturally occurring phenomenon which can be greatly enhanced by introducing longitudinal vortex generators (VGs). As the longitudinal vortices can potentially enhance heat transfer with small pressure loss penalty, VGs are widely used to enhance the heat transfer of flat-plate type heat exchangers. However, there are few researches which deal with its thermal optimization. Three dimensional numerical simulations are performed to study the effect of angle of attack and attach angle (angle between VG and wall) of vortex generator on the fluid flow and heat transfer characteristics of a flat-plate channel. The flow is assumed as steady state, incompressible and laminar within the range of studied Reynolds numbers (Re = 380, 760, 1140). In the present work, the average and local Nusselt number and pressure drop are investigated for Rectangular vortex generator (RVG) with varying angle of attack and attach angle. The numerical results indicate that the heat transfer and pressure drop increases with increasing the angle of attack to a certain range and then decreases with increasing angle of attack. Moreover, the attach angle also plays an importance role; a 90° attach angle is not necessary for enhancing the heat transfer. Usually, heat transfer enhancement is achieved at the expense of pressure drop penalty. To find the optimal position of vortex generator to obtain maximum heat transfer and minimum pressure drop, the data obtained from numerical simulations are used to train a BRANN (Bayesian-regularized artificial neural network). This in turn is used to drive multi-objective genetic algorithm (MOGA) to find the optimal parameters of VGs in the form of Pareto front. The optimal values of these parameters are finally presented.

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2D Numerical Simulation Study of Airfoil Performance

10.5194/wes-2021-45 ◽

2021 ◽

Author(s):

Nasser Shelil

Keyword(s):

Experimental Data ◽

Wind Tunnel ◽

Air Temperature ◽

Wind Turbines ◽

Aerodynamic Force ◽

Angle Of Attack ◽

Turbulence Models ◽

Aerodynamic Characteristics ◽

Operating Conditions ◽

Ansys Fluent

Abstract. The aerodynamic characteristics of DTU-LN221 airfoil is studied. ANSYS Fluent is used to simulate the airfoil performance with seven different turbulence models. The simulation results for the airfoil with different turbulence models are compared with the wind tunnel experimental data performed under the same operating conditions. It is found that there is a good agreement between the computational fluid dynamics (CFD) predicted aerodynamic force coefficients with wind tunnel experimental data especially with angle of attack between −5° to 10°. RSM is chosen to investigate the flow field structure and the surface pressure coefficients under different angle of attack between −5° to 10°. Also the effect of changing air temperature, velocity and turbulence intensity on lift and drag coefficients/forces are examined. The results show that it is recommended to operate the wind turbines airfoil at low air temperature and high velocity to enhance the performance of the wind turbines.

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

Mobile Information Systems ◽

10.1155/2021/3691559 ◽

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.

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