Alula-Inspired Leading Edge Device for Low Reynolds Number Flight

2016 ◽  
Author(s):  
Boris A. Mandadzhiev ◽  
Michael K. Lynch ◽  
Leonardo P. Chamorro ◽  
Aimy A. Wissa
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Tip Vortex ◽  
Relative Angle ◽  
Lift And Drag

Robust and predictable aerodynamic performance of unmanned aerial vehicles at the limits of their design envelope is critical for safety and mission adaptability. In order for a fixed wing aircraft to maintain the lift necessary for sustained flight at very low speeds and large angles of attack (AoA), the wing shape has to change. This is often achieved by using deployable aerodynamic surfaces, such as flaps or slats, from the wing leading or trailing edges. In nature, one such device is a feathered structure on birds’ wings called the alula. The span of the alula is 5% to 20% of the wing and is attached to the first digit of the wing. The goal of the current study is to understand the aerodynamic effects of the alula on wing performance. A series of wind tunnel experiments are performed to quantify the effect of various alula deployment parameters on the aerodynamic performance of a cambered airfoil (S1223). A full wind tunnel span wing, with a single alula located at the wing mid-span is tested under uniform low-turbulence flow at three Reynolds numbers, Re = 85,000, 106,00 and 146,000. An experimental matrix is developed to find the range of effectiveness of an alula-type device. The alula relative angle of attack measured measured from the mean chord of the airfoil is varied to modulate tip-vortex strength, while the alula deflection is varied to modulate the distance of the tip vortex to the wing surface. Lift and drag forces were measured using a six axis force transducer. The lift and drag coefficients showed the greatest sensitivity to the the alula relative angle of attack, increasing the normalized lift coefficient by as much as 80%. Improvements in lift are strongly correlated to higher alula angle, with β = 0° – 5°, while reduction in the drag coefficient is observed with higher alula tip deflection ratios and lower β angles. Results show that, as the wing angle of attack and Reynolds number are increased, the overall lift co-efficient improvement is diminished while the reduction in drag coefficient is higher.

Experimental investigation of ground effects on aerodynamics of sinusoidal leading-edge wings

2020 ◽  
pp. 095440622097542
Author(s):  
AA Mehraban ◽  
MH Djavareshkian
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Research Study ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Wide Range ◽  
Ground Effects

Sinusoidal leading-edge wings have attracted many considerations since they can delay the stall and enhance the maneuverability. The main contribution of this research study is to experimentally investigate effects of ground on aerodynamic performance of sinusoidal leading-edge wings. To this end, 6 tubercled wings with different amplitudes and wavelengths are fabricated and compared with the baseline wing which has smooth leading-edge. Proposed wings are tested in different distances from the ground in a wind tunnel lab for a wide range of angle of attack from 0° to 36° and low Reynolds number of 45,000. Results indicated that lift coefficient is improved when wings get close to the ground. Furthermore, increment of protuberance amplitude in the vicinity of the ground could efficiently prevent stalling particularly for shorter wavelength.

Experimental Aerodynamic Characteristics of a Compound Wing in Ground Effect

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Saeed Jamei ◽  
Adi Maimun Abdul Malek ◽  
Shuhaimi Mansor ◽  
Nor Azwadi Che Sidik ◽  
Agoes Priyanto
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Center Of Pressure ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Ground Effect ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Ground Clearance

Wing configuration is a parameter that affects the performance of wing-in-ground effect (WIG) craft. In this study, the aerodynamic characteristics of a new compound wing were investigated during ground effect. The compound wing was divided into three parts with a rectangular wing in the middle and two reverse taper wings with anhedral angle at the sides. The sectional profile of the wing model is NACA6409. The experiments on the compound wing and the rectangular wing were carried to examine different ground clearances, angles of attack, and Reynolds numbers. The aerodynamic coefficients of the compound wing were compared with those of the rectangular wing, which had an acceptable increase in its lift coefficient at small ground clearances, and its drag coefficient decreased compared to rectangular wing at a wide range of ground clearances, angles of attack, and Reynolds numbers. Furthermore, the lift to drag ratio of the compound wing improved considerably at small ground clearances. However, this improvement decreased at higher ground clearance. The drag polar of the compound wing showed the increment of lift coefficient versus drag coefficient was higher especially at small ground clearances. The Reynolds number had a gradual effect on lift and drag coefficients and also lift to drag of both wings. Generally, the nose down pitching moment of the compound wing was found smaller, but it was greater at high angle of attack and Reynolds number for all ground clearance. The center of pressure was closer to the leading edge of the wing in contrast to the rectangular wing. However, the center of pressure of the compound wing was later to the leading edge at high ground clearance, angle of attack, and Reynolds number.

scholarly journals Lift and Drag Coefficient Map of NACA4415 Airfoil

2021 ◽  
Vol 2076 (1) ◽  
pp. 012066
Author(s):  
Rui Yin ◽  
Jing Huang ◽  
Zhi-Yuan He
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Optimal Angle ◽  
Fluent Software ◽  
Lift And Drag ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Abstract The NACA4415 airfoil was numerically simulated with the help of the Fluent software to analyze its aerodynamic characteristics. Results are acquired as follows: The calculation accuracy of Fluent software is much higher than that of XFOIL software; the calculation result of SST k-ω(sstkw) turbulence model is closest to the experimental value; within a certain range, the larger the Reynolds number is, the larger the lift coefficient and lift-to-drag ratio of the airfoil will be, and the smaller the drag coefficient will be; when the angle of attack is less than the optimal angle of attack, the Reynolds number has less influence on the lift-to-drag coefficient and the lift-to-drag ratio; as the Reynolds number increases, the optimal angle of attack increases slightly, and the applicable angle of attack range for high lift-to-drag ratios becomes smaller.

Numerical Simulation of Flow Past an Elliptical Cylinder Undergoing Rotationally Oscillating Motion

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Esam M. Alawadhi
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Strouhal Number ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Local Maximum ◽  
Elliptical Cylinder ◽  
Equivalent Diameter ◽  
Lift And Drag ◽  
Oscillating Motion

The finite element method is used to simulate the near-wake of an elliptical cylinder undergoing rotationally oscillating motion at low Reynolds number, 50 ≤ Re ≤ 150. Reynolds number is based on equivalent diameter of the ellipse. The rotationally oscillating motion was carried out by varying the angle of attack between 10 deg and 60 deg, while the considered oscillation frequencies are between St/4 and 4 × St, where St is the Strouhal number of a stationary elliptical cylinder with zero angle of attack. Fluid flow results are presented in terms of lift and drag coefficients for rotationally oscillating case. The details of streamlines and vorticity contours are also presented for a few representative cases. The result indicates that at when the frequency is equal to the Strouhal number, the root-mean-square (RMS) of lift coefficient reaches its local minimum, while the average of drag coefficient reaches its local maximum. Increasing the Reynolds number increases the RMS of lift coefficient and decreases average of drag coefficient.

Experimental investigations of flow over NACA airfoils 0021 and 4412 of wind turbine blades with and without Tubercles

2021 ◽  
pp. 0309524X2110071
Author(s):  
Usman Butt ◽  
Shafqat Hussain ◽  
Stephan Schacht ◽  
Uwe Ritschel
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Wind Turbine ◽  
Critical Region ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Wind Turbine Blades

Experimental investigations of wind turbine blades having NACA airfoils 0021 and 4412 with and without tubercles on the leading edge have been performed in a wind tunnel. It was found that the lift coefficient of the airfoil 0021 with tubercles was higher at Re = 1.2×105 and 1.69×105 in post critical region (at higher angle of attach) than airfoils without tubercles but this difference relatively diminished at higher Reynolds numbers and beyond indicating that there is no effect on the lift coefficients of airfoils with tubercles at higher Reynolds numbers whereas drag coefficient remains unchanged. It is noted that at Re = 1.69×105, the lift coefficient of airfoil without tubercles drops from 0.96 to 0.42 as the angle of attack increases from 15° to 20° which is about 56% and the corresponding values of lift coefficient for airfoil with tubercles are 0.86 and 0.7 at respective angles with18% drop.

scholarly journals Numerical simulation of flapping airfoil with alula

2020 ◽  
Vol 12 ◽  
pp. 175682932097798
Author(s):  
Han Bao ◽  
Wenqing Yang ◽  
Dongfu Ma ◽  
Wenping Song ◽  
Bifeng Song
Keyword(s):  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Geometric Parameters ◽  
Flight Performance ◽  
Relative Angle ◽  
Vertical Distance ◽  
Unsteady Effect ◽  
Flapping Airfoil

Bionic micro aerial vehicles have become popular because of their high thrust efficiency and deceptive appearances. Leading edge or trailing edge devices (such as slots or flaps) are often used to improve the flight performance. Birds in nature also have leading-edge devices, known as the alula that can improve their flight performance at large angles of attack. In the present study, the aerodynamic performance of a flapping airfoil with alula is numerically simulated to illustrate the effects of different alula geometric parameters. Different alula relative angles of attack β (the angle between the chord line of the alula and that of the main airfoil) and vertical distances h between the alula and the main airfoil are simulated at pre-stall and post-stall conditions. Results show that at pre-stall condition, the lift increases with the relative angle of attack and the vertical distance, but the aerodynamic performance is degraded in the presence of alula compared with no alula, whereas at post-stall condition, the alula greatly enhances the lift. However, there seems to be an optimal relative angle of attack for the maximum lift enhancement at a fixed vertical distance considering the unsteady effect, which may indicate birds can adjust the alula twisting at different spanwise positions to achieve the best flight performance. Different alula geometric parameters may affect the aerodynamic force by modifying the pressure distribution along the airfoil. The results are instructive for design of flapping-wing bionic unmanned air vehicles.

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.

Analysis of Vortex-Induced Vibration of Riser using Spalart-Almaras Model

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Jaswar Koto ◽  
Abdul Khair Junaidi
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Vortex Shedding ◽  
Lift Coefficient ◽  
Offshore Structures ◽  
The Other ◽  
Main Concern ◽  
Vortex Induced Vibration ◽  
Simulation Results ◽  
Lift And Drag

Vortex-induced vibration is natural phenomena where an object is exposed to moving fluid caused vibration of the object. Vortex-induced vibration occurred due to vortex shedding behind the object. One of the offshore structures that experience this vortex-induced vibration is riser. The riser experience vortex-induced vibration due to vortex shedding caused by external load which is sea current. The effect of this vortex shedding to the riser is fatigue damage. Vortex-induced vibration of riser becomes the main concern in oil and gas industry since there will be a lots of money to be invested for the installation and maintenance of the riser. The previous studies of this vortex-induced vibration have been conducted by experimental method and Computational Fluid Dynamics (CFD) method in order to predict the vortex shedding behaviour behind the riser body for the determination of way to improve the riser design. This thesis represented the analysis of vortex induced vibration of rigid riser in two-dimensional. The analysis is conducted using Computational Fluid Dynamic (CFD) simulations at Reynolds number at 40, 200, 1000, and 1500. The simulations were performed using Spalart-Allmaras turbulent model to solve the transport equation of turbulent viscosity. The simulations results at Reynolds number 40 and 200 is compared with the other studies for the validation of the simulation, then further simulations were conducted at Reynolds number of 1000 and 1500. The coefficient of lift and drag were obtained from the simulations. The comparison of lift and drag coefficient between the simulation results in this study and experiment results from the other studies showed good agreement. Besides that, the in-line vibration and cross-flow vibration at different Reynolds number were also investigated. The drag coefficient obtained from the simulation results remain unchanged as the Reynolds number increased from 200 to 1500. The lift coefficient obtained from the simulations increased as the Reynolds number increased from 40 to 1500.

Aerodynamic Characteristics of a Deformable Membrane Aerofoil

2014 ◽  
Vol 553 ◽  
pp. 255-260
Author(s):  
Viktor Šajn ◽  
Igor Petrović ◽  
Franc Kosel
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Lift Coefficient ◽  
Fluid Structure Interaction ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Relative Difference ◽  
Structure Interaction ◽  
Deformable Membrane

In the paper, numerical and experimental study of low Reynolds number airflow around the deformable membrane airfoil (DMA) is presented. Simulations of a fluid-structure interaction between the fluid and the DMA were performed. In the experiment, the DMA model was made from a thin PVC sheet, which was wrapped around the steel rod at the leading and trailing edge. Measurements were performed in a wind tunnel at a chord Reynolds number of 85.7·103, over the angle of attack range from 0° to 15° and DMA shortening ratio from 0.025 to 0.150. Simulations were in an agreement with the experiment, since the average relative difference of coefficient of lift was smaller than 7.3%. For the same value of Reynolds number, DMA shows improved lift coefficient Cy= 2.18, compared to standard rigid airfoils.

Drag and lift measurements of solid sports balls in still air

2017 ◽  
Vol 232 (3) ◽  
pp. 255-263 ◽  
Author(s):  
Jeff R Kensrud ◽  
Lloyd V Smith
Keyword(s):  
Surface Roughness ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Rough Surface ◽  
Lift Coefficient ◽  
Laboratory Setting ◽  
Air Drag ◽  
High Speeds ◽  
Drag And Lift ◽  
Lift And Drag

The following article considers lift and drag measurements of solid sports balls propelled through still air in a laboratory setting. The balls traveled at speeds ranging from 26 to 134 m/s with spin rates up to 3900 r/min. Light gates measured the speed and location of the balls at two locations from which lift and drag values were determined. Ball roughness varied from polished to rough surface protrusions, that is, seams as high as 1.5 mm. Lift and drag were observed to depend on speed, spin rate, surface roughness, and seam orientation. A drag crisis was observed on smooth balls as well as non-rotating seamed balls with seam heights less than 0.9 mm. The drag coefficient of approximately 0.42 was nearly constant with speed for spinning seamed balls with seam height greater than 0.9 mm. The still air drag coefficient of smooth balls was comparable to wind tunnel drag at low speeds ( Re < 2 × 105) and higher than wind tunnel results at high speeds ( Re > 2 × 105). The lift and drag coefficients of spinning balls increased with increasing spin rate. The lift coefficient of baseballs was not sensitive to ball orientation or seam height.

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