Aerodynamic Investigations of Low-Aspect-Ratio Thin Plate Wings at Low Reynolds Numbers

Abstract

To 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 10 4 and 10 5 . 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 nearwake 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.

The Performance Test of Three Different Horizontal Axis Wind Turbine (HAWT) Blade Shapes Using Experimental and Numerical Methods

“…The pressure transducer was calibrated using a micro manometer and certified. The flow speed in the test section was then calculated using the incompressible steady Bernoulli's equation [19]. In the wind tunnel experiments, the area ratio is defined as A b /A w , where A b is the blade swept area and A w is the cross section area of the wind tunnel test section.…”

Effect of Thickness-to-Chord Ratio on Flow Structure of a Low Swept Delta Wing

“…Gursul et al [1] used flow visualization technique to observe the vortex by providing smoke or dye to the flow field. In another study, Lambourne and Bryer [53] clarified the phenomenon over a slender delta wing with a sweep angle of Λ=65 o , in Figure 2.4. Erickson [24] also concluded that observations of the breakdown location in wind tunnel were in line with real flight observations.…”

Plasma-Based Dynamic Stall Control and Modeling on an Aspect-Ratio-One Wing

“…In particular, wing stall with accompanying bi-stable flow states (sometimes called hysteresis), triggered by bursting of the leading-edge separation bubble (LSB), should be avoided [6]. In contrast to airfoils and high-aspect-ratio wings, lift generation on low AR wings at high angles of attack is generated predominantly by wingtip vortices [7][8][9][10][11]. Although the majority of low AR investigations consider thin-plate-type wings [7][8][9][10][11], conventional wing profiles offer the critically important advantage of storage volume [12,13].…”

“…In contrast to airfoils and high-aspect-ratio wings, lift generation on low AR wings at high angles of attack is generated predominantly by wingtip vortices [7][8][9][10][11]. Although the majority of low AR investigations consider thin-plate-type wings [7][8][9][10][11], conventional wing profiles offer the critically important advantage of storage volume [12,13]. This has served as motivation to conduct basic research on conventional (non-flat-plate) profiles with rectangular planforms [14][15][16].…”