Experimental validation of numerical decambering approach for flow past a rectangular wing
06 Apr 2020-Vol. 234, Iss: 9, pp 1564-1582
TL;DR: Experimental investigation on two rectangular wings with NACA0012 and NACA4415 profiles was performed at different Reynolds numbers to understand their aerodynamic behaviours at a high α regime as mentioned in this paper.
Abstract: Experimental investigation on two rectangular wings with NACA0012 and NACA4415 profiles is performed at different Reynolds numbers to understand their aerodynamic behaviours at a high α regime. In-...
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28 Jan 2022-Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science
TL;DR: In this paper , the performance of the biomimetic wing is compared with rectangular and elliptical wings at low Reynolds number (Re) ranging from 2.5 × 104 to 1 × 105.
Abstract: A biomimetic wing is designed by considering the wing of a natural flyer (Passer domesticus) as a reference. Since the birds have thin wings, Bergey BW-3, a thin and highly cambered airfoil, is used to design the wing cross section. To investigate the aerodynamic characteristics of the biomimetic wing, numerical and experimental studies are carried out at low Reynolds number (Re) ranging from 2.5 × 104 to 1 × 105. It is observed that the numerical findings have the similar trend as that of the experimental observations. The performance of the biomimetic wing is compared with rectangular and elliptical wings at Re = 5 × 104. It is observed that the separation bubble formed over the surface of the biomimetic wing at Re = 2.5 × 104 is not strong enough to influence the lift coefficient but increases the drag coefficient dramatically when the mean angle of attack exceeds 18°. It is observed that the drop in the lift coefficient of rectangular wing is higher than that of the other wings due to the presence of sharp edges in the planform. The lowest drag coefficient is witnessed in the elliptical wing but it also has the lowest lift coefficient due to the interaction between the separation bubble and tip vortices. On the other hand, the biomimetic wing offers the highest lift coefficient with a considerable amount of drag. Overall, a 57.9% increase in lift coefficient is observed for the biomimetic wing than that of the elliptical wing under the same conditions. A 22.4% increase in the lift to drag ratio of the biomimetic wing is observed over that of the rectangular wing. It is also observed that the flow separates dramatically as the mean angle of attack increases beyond the stall angle in the rectangular and elliptical wings. But a delay in the flow separation is observed in case of the biomimetic wing after the stall angle. It is also observed that the suction over the wing surface of the biomimetic wing is more at the wing root (fixed end) than that at the wing tip (free end), which may provide good stability during flight conditions. The enhanced aerodynamic performance of the biomimetic wing is due to change in shape of the wing along the span which has a strong influence over its effective angle of attack with respect to the incoming flow.
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TL;DR: In this paper, numerical analysis is conducted using a local camber correction approach called "decambering" to predict pre and post-stall aerodynamic characteristics of multiple lifting surfaces operating in formation.
Abstract: In this paper, numerical analysis is conducted using a local camber correction approach called “decambering” to predict pre and post-stall aerodynamic characteristics of multiple lifting surfaces operating in formation. A three wings Chevron formation and five and nine wings V-formation are studied. NACA2412 wing section is used and experimental validation is provided with Cessna 172 aircrafts flying in Chevron formation. Effect of wing incidence and shifting of stall angles is looked at along with changes in geometric offsets between the wings in formation. The spanwise distribution of coefficients of lift and induced drag at different angles of attack, including high and post-stall angles of attack is studied for all the wings. The span efficiency factor, which represents the correction in drag due to change in lift as compared to that of an ideal wing of the same aspect ratio but with elliptical lift distribution is calculated. The maximum possible efficiency is then used to estimate the maximum reduction in drag possible for individual wings in different formations. The change in efficiency with number of lifting surfaces in a formation is also estimated.
TL;DR: In this article , the authors investigated the effect of two types of winglets, multi-tip and raked, on the performance of sinusoidal and simple leading-edge wings and compared it by a numerical method.
Abstract:
Purpose
This study aims to investigate the effectiveness of two types of winglets, multi-tip and raked, on the performance of sinusoidal and simple leading-edge wings and compares it by a numerical method.
Design/methodology/approach
The wing configuration in this study is rectangular and uses NACA0020 section, and all simulations are performed by a numerical method based on finite volume and base pressure algorithm in Reynolds 2 × [10]^5. In the mentioned numerical method, the flow is considered turbulent, and the k-ω-SST model is used. To calculate the stresses on the wing surface, the mesh is extended to below the viscous layer, and a second-order upstream accuracy is used to calculate the convection flux.
Findings
The use of raked and multi-tip winglets for the sinusoidal edge of the wing improved aerodynamic performance by 5.12 and 2.28%, respectively, and the greatest effect of these two winglets was on increasing the lifting force and reducing the inductive drag, respectively. Also, by examining the distribution of induced vortices around the configurations, it was found that the curvature of the sinusoidal wing tip at the angles of attack before stall reduced the strength of the induced vortices and, the use of winglet during and after stall, caused increased aerodynamic performance of the sinusoidal wing.
Practical implications
The whale is an international species of aquatic animal found in most of the world’s oceans. It has large fin aspect ratios that have a series of bulges at the edge of the attack, which improves the aerodynamic performance near and after stall. Today, one of the fields of research is the use of this idea in the wings of micro air vehicle.
Originality/value
Winglet reduces induced drag in simple wings. So far, the effect of winglets on wings with sinusoidal attack edges has not been investigated.
References
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Journal Article•
7,568 citations
01 Jan 1989
TL;DR: In this article, an inviscid linear-vorticity panel method with a Karman-Tsien compressiblity correction is developed for direct and mixed-inverse modes.
Abstract: Calculation procedures for viscous/inviscid analysis and mixed-inverse design of subcritical airfoils are presented. An inviscid linear-vorticity panel method with a Karman-Tsien compressiblity correction is developed for direct and mixed-inverse modes. Source distributions superimposed on the airfoil and wake permit modeling of viscous layer influence on the potential flow. A two-equation lagged dissipation integral method is used to represent the viscous layers. Both laminar and turbulent layers are treated, with an e 9-type amplification formulation determinining the transition point. The boundary layer and transition equations are solved simultaneously with the inviscid flowfield by a global Newton method. The procedure is especially suitable for rapid analysis of low Reynolds number airfoil flows with transitional separation bubbles. Surface pressure distributions and entire polars are calculated and compared with experimental data. Design procedure examples are also presented.
2,185 citations
804 citations
688 citations
TL;DR: In this paper, the authors measured the lift, drag, and pitching moment about the quarter chord on a series of thin flat plates and cambered plates at chord Reynolds numbers varying between 60,000 and 200,000.
Abstract: The design of micro aerial vehicles requires a better understanding of the aerodynamics of small low-aspect-ratio wings An experimental investigation has focused on measuring the lift, drag, and pitching moment about the quarter chord on a series of thin flat plates and cambered plates at chord Reynolds numbers varying between 60,000 and 200,000 Results show that the cambered plates offer better aerodynamic characteristics and performance It also appears that the trailing-edge geometry of the wings and the turbulence intensity in the wind tunnel do not have a strong effect on the lift and drag for thin wings at low Reynolds numbers Moreover, the results did not show the presence of any hysteresis, which is usually observed with thick airfoils/wings
369 citations