Low Reynolds Number Aerodynamics of Low-Aspect-Ratio, Thin/Flat/Cambered-Plate Wings
01 Sep 2000-Journal of Aircraft (American Institute of Aeronautics and Astronautics (AIAA))-Vol. 37, Iss: 5, pp 825-832
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
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TL;DR: In this article, the aerodynamic problems that must be addressed in order to design a successful small aerial vehicle are described, including the effects of Reynolds number and aspect ratio (AR) on the design and performance of fixed-wing vehicles.
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Cites background from "Low Reynolds Number Aerodynamics of..."
...Recently, Pelletier & Mueller (2000) and Mueller A n n u ....
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TL;DR: In this paper, the influence of aspect ratio, angle of attack and planform geometry on the wake vortices and the resulting forces on the plate was investigated for three-dimensional flows over impulsively translated low-aspect-ratio flat plates.
Abstract: Three-dimensional flows over impulsively translated low-aspect-ratio flat plates are investigated for Reynolds numbers of 300 and 500, with a focus on the unsteady vortex dynamics at post-stall angles of attack. Numerical simulations, validated by an oil tow-tank experiment, are performed to study the influence of aspect ratio, angle of attack and planform geometry on the wake vortices and the resulting forces on the plate. Immediately following the impulsive start, the separated flows create wake vortices that share the same topology for all aspect ratios. At large time, the tip vortices significantly influence the vortex dynamics and the corresponding forces on the wings. Depending on the aspect ratio, angle of attack and Reynolds number, the flow at large time reaches a stable steady state, a periodic cycle or aperiodic shedding. For cases of high angles of attack, an asymmetric wake develops in the spanwise direction at large time. The present results are compared to higher Reynolds number flows. Some non-rectangular planforms are also considered to examine the difference in the wakes and forces. After the impulsive start, the time at which maximum lift occurs is fairly constant for a wide range of flow conditions during the initial transient. Due to the influence of the tip vortices, the three-dimensional dynamics of the wake vortices are found to be quite different from the two-dimensional von Karman vortex street in terms of stability and shedding frequency.
354 citations
Cites background from "Low Reynolds Number Aerodynamics of..."
...The shape of the leading or trailing edge (sharp or rounded) has been found to result in no important change in the lift and drag coefficients aside from some difference in the momentum coefficient at higher Reynolds numbers of O(104–105) (Pelletier & Mueller 2000; Torres & Mueller 2004)....
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TL;DR: In this article, a study of the lift, drag, and pitching moment characteristics of low aspect ratio operating at low Reynolds numbers is presented, which includes comparison of lift-curve slope, nonlinear equation approximations, maximum lift coefficient, and center of lift.
Abstract: The recent interest in the development of small unmanned aerial vehicles (UAVs) and micro air vehicles has revealed a need for a more thorough understanding of the aerodynamics of small airplanes flying at low speeds. In response to this need, a study of the lift, drag, and pitching moment characteristics of wings of low aspect ratio operating at low Reynolds numbers are presented. Wind-tunnel tests of wings with aspect ratios between 0.5 and 2.0, four distinct planforms, thickness-to-chord ratios of ≈ 2%, and 5-to-1 elliptical leading edges have been conducted as part of this research. The Reynolds numbers considered were in the range of 7 × × 10 4 to 2 × × 10 5 . Analysis of the data includes comparison of lift-curve slope, nonlinear equation approximations, maximum lift coefficient, and center of lift.
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References
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Journal Article•
7,568 citations
Book•
01 Feb 1986
TL;DR: In this article, Navier-Stokes et al. discuss the fundamental principles of Inviscid, Incompressible Flow over airfoils and their application in nonlinear Supersonic Flow.
Abstract: TABLE OF CONTENTS Preface to the Fifth Edition Part 1: Fundamental Principles 1. Aerodynamics: Some Introductory Thoughts 2. Aerodynamics: Some Fundamental Principles and Equations Part 2: Inviscid, Incompressible Flow 3. Fundamentals of Inviscid, Incompressible Flow 4. Incompressible Flow Over Airfoils 5. Incompressible Flow Over Finite Wings 6. Three-Dimensional Incompressible Flow Part 3: Inviscid, Compressible Flow 7. Compressible Flow: Some Preliminary Aspects 8. Normal Shock Waves and Related Topics 9. Oblique Shock and Expansion Waves 10. Compressible Flow Through Nozzles, Diffusers and Wind Tunnels 11. Subsonic Compressible Flow Over Airfoils: Linear Theory 12. Linearized Supersonic Flow 13. Introduction to Numerical Techniques for Nonlinear Supersonic Flow 14. Elements of Hypersonic Flow Part 4: Viscous Flow 15. Introduction to the Fundamental Principles and Equations of Viscous Flow 16. A Special Case: Couette Flow 17. Introduction to Boundary Layers 18. Laminar Boundary Layers 19. Turbulent Boundary Layers 20. Navier-Stokes Solutions: Some Examples Appendix A: Isentropic Flow Properties Appendix B: Normal Shock Properties Appendix C: Prandtl-Meyer Function and Mach Angle Appendix D: Standard Atmosphere Bibliography Index
3,113 citations
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01 Jan 1966
TL;DR: The use of wind tunnel data for aerodynamic experiments has been studied in this article, where three dimensions of three-dimensional flow and pressure, flow, and shear stress measurements are used to calibrate the test section.
Abstract: Wind Tunnels Wind Tunnel Design Pressure, Flow, and Shear Stress Measurements Flow Visualization Calibration of the Test Section Forces and Moments from Balance Measurements Use of Wind Tunnel Data: Scale Effects Boundary Corrections I: Basics and Two- Dimensional Cases Boundary Corrections II: Three-Dimensional Flow Boundary Corrections III: Additional Applications Additional Considerations for Aerodynamic Experiments Aircraft and Aircraft Components Ground Vehicles Marine Vehicles Wind Engineering Small Wind Tunnels Dynamic Tests Appendices Index
1,828 citations
TL;DR: In this article, a planform wing was tested at Reynolds numbers as low as 20 000 in a low turbulence wind tunnel and the best profile was a thin plate with a 5% circular arc camber.
Abstract: Rectangular planform wings were tested at Reynolds numbers as low as 20 000 in a low turbulence wind tunnel. The lift and drag measurements on a NACA 0012 profile were compared with those for thin flat and cambered plates. For all Reynolds numbers below 70 000 the best profile was a thin plate with a 5% circular arc camber. At all turbulence levels this profile produced the greatest lift-drag ratio, and had the highest lift coefficient at all angles of attack. The 5% camber and all of the thin plates tested were relatively insensitive to either a variation in the Reynolds number, or an increase in the wind tunnel turbulence level, whereas the NACA 0012 was very seriously affected by either, at Reynolds numbers below 50 000.
234 citations