scholarly journals Wind-Tunnel Measurement of Differential Pressure on the Surface of a Dynamically Inflatable Wing Cell

Aerospace ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 34
Author(s):  
Diego Muniz Benedetti ◽  
Carlos Alberto Gurgel Veras
Keyword(s):  
Wind Tunnel ◽  
Leading Edge ◽  
Flight Test ◽  
Aerodynamic Characteristics ◽  
Pressure Differential ◽  
Local Pressure ◽  
Recirculation Bubble ◽  
Novel Approach ◽  
Coefficients Of Variation ◽  
Air Intake

An instrumentation system for in-situ measurement of the inner-outer pressure differential at the upper and lower surfaces of dynamically inflatable wings is designed and tested, revealing important insights into the aerodynamic characteristics of inflatable airfoils. Wind tunnel tests demonstrated full capability of low-pressure differential readings in the range of 1.0–120 Pa, covering speeds from 3 to 10 m/s at angles of attack from −20 to +25°. Readings were stable, presenting coefficients of variation from 2% to 7% over the operational flight envelope. The experimental data confirmed the occurrence of a bottom leading-edge recirculation bubble, linked to the low Reynolds regime and the presence of an air intake. It supported the proposition of a novel approach to aerodynamic characterization based on local pressure differentials, which takes in account the confined airflow structure and provides lift forces estimations compatible with practical observation. The results were also compatible with data previously obtained following different strategies and were shown to be effective for parameterizing the inflation and stall phenomena. Overall, the instrumentation may be applied straightforwardly as a flight-test equipment, and it can be further converted into collapse alert and prevention systems.

An experimental parametric study on planar sheared wings tip devices for low-to-moderate aspect ratio wings

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Lourelay Moreira dos Santos ◽  
Guilherme Ferreira Gomes ◽  
Rogerio F. Coimbra
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Parametric Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Sweep Angle ◽  
Wind Tunnel Tests ◽  
Content Type ◽  
Wing Tips ◽  
Wing Tip

Purpose The purpose of this study is to investigate the aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips. Design/methodology/approach In this work, wind tunnel tests were made to study the influence in aerodynamic characteristics over a typical low-to-moderate-aspect-ratio wing of a general aviation aircraft, equipped with sheared – swept and tapered planar – wing tips. An experimental parametric study of different wing tips was tested. Variations in its leading and trailing edge sweep angle as well as variations in wing tip taper ratio were considered. Sheared wing tips modify the flow pattern in the outboard region of the wing producing a vortex flow at the wing tip leading edge, enhancing lift at high angles of attack. Findings The induced drag is responsible for nearly 50% of aircraft total drag and can be reduced through modifications to the wing tip. Some wing tip models present complex geometries and many of them present benefits in particular flight conditions. Results have demonstrated that sweeping the wing tip leading edge between 60 and 65 degrees offers an increment in wing aerodynamic efficiency, especially at high lift conditions. However, results have demonstrated that moderate wing tip taper ratio (0.50) has better aerodynamic benefits than highly tapered wing tips (from 0.25 to 0.15), even with little less wing tip leading edge sweep angle (from 57 to 62 degrees). The moderate wing tip taper ratio (0.50) offers more wing area and wing span than the wings with highly tapered wing tips, for the same aspect ratio wing. Originality/value Although many studies have been reported on the aerodynamics of wing tips, most of them presented complex non-planar geometries and were developed for cruise flight in high subsonic regime (low lift coefficient). In this work, an exploration and parametric study through wind tunnel tests were made, to evaluate the influence in aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips (wing tips highly swept and tapered).

Modification of the NACA 632-415 Leading Edge for Better Aerodynamic Performance

2002 ◽  
Vol 124 (4) ◽  
pp. 327-334 ◽  
Author(s):  
Christian Bak ◽  
Peter Fuglsang
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Power Level ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Dynamic Stall ◽  
Wind Tunnel Tests ◽  
Damping Characteristics ◽  
Edge Roughness ◽  
Drag Ratio

Double stall causes more than one power level when stall-regulated wind turbines operate in stall. This involves significant uncertainty on power production and loads. To avoid double stall, a new leading edge was designed for the NACA 632-415 airfoil, an airfoil that is often used in the tip region of wind turbines. A numerical optimization tool incorporating XFOIL was used with a special formulation for the airfoil leading edge shape. The EllipSys2D CFD code was used to analyze the modified airfoil. In theory and in wind tunnel tests, the modified airfoil showed smooth and stable stall characteristics with no tendency to double stall. Also, both theory and wind tunnel tests showed that the overall aerodynamic characteristics were similar to NACA 632-415 except for an increase in the lift-drag ratio below maximum lift and an increase in maximum lift. The wind tunnel tests showed that dynamic stall and aerodynamic damping characteristics for the modified airfoil and the NACA 632-415 airfoil were the same. The modified airfoil with leading edge roughness in general had better characteristics compared with the NACA 632-415 airfoil.

scholarly journals Experimental Study on Aerodynamic Characteristics of a Gurney Flap on a Wind Turbine Airfoil under High Turbulent Flow Condition

2020 ◽  
Vol 10 (20) ◽  
pp. 7258 ◽  
Author(s):  
Junwei Yang ◽  
Hua Yang ◽  
Weijun Zhu ◽  
Nailu Li ◽  
Yiping Yuan
Keyword(s):  
Wind Tunnel ◽  
Turbulent Flow ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Chord Length ◽  
Turbulence Level ◽  
Gurney Flaps ◽  
Gurney Flap ◽  
Delay Phenomenon

The objective of the current work is to experimentally investigate the effect of turbulent flow on an airfoil with a Gurney flap. The wind tunnel experiments were performed for the DTU-LN221 airfoil under different turbulence level (T.I. of 0.2%, 10.5% and 19.0%) and various flap configurations. The height of the Gurney flaps varies from 1% to 2% of the chord length; the thickness of the Gurney flaps varies from 0.25% to 0.75% of the chord length. The Gurney flap was vertical fixed on the pressure side of the airfoil at nearly 100% measured from the leading edge. By replacing the turbulence grille in the wind tunnel, measured data indicated a stall delay phenomenon while increasing the inflow turbulence level. By further changing the height and the thickness of the Gurney flap, it was found that the height of the Gurney flap is a very important parameter whereas the thickness parameter has little influence. Besides, velocity in the near wake zone was measured by hot-wire anemometry, showing the mechanisms of lift enhancement. The results demonstrate that under low turbulent inflow condition, the maximum lift coefficient of the airfoil with flaps increased by 8.47% to 13.50% (i.e., thickness of 0.75%), and the Gurney flap became less effective after stall angle. The Gurney flap with different heights increased the lift-to-drag ratio from 2.74% to 14.35% under 10.5% of turbulence intensity (i.e., thickness of 0.75%). However, under much a larger turbulence environment (19.0%), the benefit to the aerodynamic performance was negligible.

scholarly journals The Effect of Rigging Angle on Longitudinal Direction Motion of Parafoil-Type Vehicle: Basic Stability Analysis and Wind Tunnel Test

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Takahiro Moriyoshi ◽  
Kazuhiko Yamada ◽  
Hiroyuki Nishida
Keyword(s):  
Stability Analysis ◽  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Leading Edge ◽  
Longitudinal Direction ◽  
Aerodynamic Characteristics ◽  
Vehicle Stability ◽  
Flexible Wings ◽  
Allowable Range ◽  
Analytical Approaches

The paraglider, a flexible flying vehicle, consists of a parafoil with flexible wings, suspension lines, and a suspended payload. At this time, the suspension lines have several parameters to be designed. Above all, a parameter called Rigging Angle (RA) is sensitive to the aerodynamic characteristics of a paraglider during flight. In this study, the effect of RA is clarified using the two-dimensional stability analysis and a wind tunnel test. The mechanisms about the parafoil-type vehicle stability are clarified through the experimental and analytical approaches as follows. The RA has an allowable range for a stable flight. When the RA is set out of the range, the parafoil cannot fly stably. Furthermore, the behavior of the parafoil wing in the case of lower RA than the allowable range is different from the case of higher RA. The parafoil collapses from the leading edge of the canopy and cannot glide in the case of lower RA.

Identification of a degradation of aerodynamic characteristics of a paraglider due to its flexibility from flight test

2019 ◽  
Vol 91 (6) ◽  
pp. 873-879 ◽  
Author(s):  
Robert Kulhánek
Keyword(s):  
High Speed ◽  
Aerodynamic Drag ◽  
Leading Edge ◽  
Flight Test ◽  
Aerodynamic Characteristics ◽  
Full Scale ◽  
Content Type ◽  
Specific Geometry ◽  
Lift And Drag ◽  
Scaled Models

Purpose Aerodynamics of paragliders is very complicated aeroelastic phenomena. The purpose of this work is to quantify the amount of aerodynamic drag related to the flexible nature of a paraglider wing. Design/methodology/approach The laboratory testing on scaled models can be very difficult because of problems in the elastic similitude of such a structure. Testing of full-scale models in a large facility with a large full-scale test section is very expensive. The degradation of aerodynamic characteristics is evaluated from flight tests of the paraglider speed polar. All aspects of the identification such as pilot and suspension lines drag and aerodynamics of spanwise chambered wings are discussed. The drag of a pilot in a harness was estimated by means of wind tunnel testing, computational fluid dynamics (CFD) solver was used to estimating smooth wing lift and drag characteristics. Findings The drag related to the flexible nature of the modern paraglider wing is within the range of 4-30 per cent of the total aerodynamic drag depending on the flight speed. From the results, it is evident that considering only the cell opening effect is sufficient at a low-speed flight. The stagnation point moves forwards towards the nose during the high speed flight. This causes more pronounced deformation of the leading edge and thus increased drag. Practical implications This paper deals with a detailed analysis of specific paraglider wing. Although the results are limited to the specific geometry, the findings help in the better understanding of the paraglider aerodynamics generally. Originality/value The data obtained in this paper are not affected by any scaling problems. There are only few experimental results in the field of paragliders on scaled models. Those results were made on simplified models at very low Reynolds number. The aerodynamic drag characteristics of the pilot in the harness with variable angles of incidence and Reynolds numbers have not yet been published.

Aerodynamic characteristics of the wings and body of a dragonfly

1996 ◽  
Vol 199 (2) ◽  
pp. 281-294 ◽  
Author(s):  
M Okamoto ◽  
K Yasuda ◽  
A Azuma
Keyword(s):  
Surface Roughness ◽  
Wind Tunnel ◽  
Flow Field ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Free Flight ◽  
Flight Tests ◽  
Dragonfly Wings ◽  
Artificial Wing

The aerodynamic characteristics of the wings and body of a dragonfly and of artificial wing models were studied by conducting two types of wind-tunnel tests and a number of free-flight tests of gliders made using dragonfly wings. The results were consistent between these different tests. The effects of camber, thickness, sharpness of the leading edge and surface roughness on the aerodynamic characteristics of the wings were characterized in the flow field with Reynolds numbers (Re) as low as 103 to 104.

Wind Tunnel Test of Effect of Sound-Absorbing Material on Lift of Two-Element Airfoil

2013 ◽  
Vol 830 ◽  
pp. 17-23
Author(s):  
Yong Wei Gao ◽  
Qi Liang Zhu ◽  
Long Wang
Keyword(s):  
Wind Tunnel ◽  
High Frequency ◽  
Lift Coefficient ◽  
Wind Tunnel Test ◽  
Low Frequency ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Fluctuating Pressure ◽  
Flow Parameters ◽  
Absorbing Material

The flow parameters of fluctuating pressure and fluctuating velocity in the gap can be changed by the porous absorption material on the leading edge of upper surface of the flap of multi-element airfoil (GAW-1),and the aerodynamic characteristics is also altered. Experiment was conducted in the NF-3 wind tunnel. It turns out that porous absorption material has a significant effect on fluctuating velocity (i.e. turbulent kinetic energy), and the lift coefficient drops when fluctuating velocity increases ; but the influence on RMS of fluctuating pressure on upper surface is not obvious; the average speed in gap is reduced. The PSD of fluctuating pressure and fluctuating velocity show that low-frequency signal has a more obvious influence on lift of multi-element airfoils than high-frequency.

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