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Tip vortex behind a wing oscillated with small amplitude

JOURNAL OF AIRCRAFT 2005年第5期42卷 1200-1208页

作者： Birch, D Lee, T McGill Univ Dept Engn Mech Montreal PQ H3A 2K6 Canada

The effect of reduced frequency on the tip vortex in the near field behind a NACA 0015 wing oscillated sinusoidally within the static-stall angle (= 14 deg) was investigated at Re = 1.86 x 10(5). The nearly symmetric vortex was observed at 0.5 to 1.5 chords downstream of the trailing edge similar to the case of a stationary wing. The oscillating wing produced a less concentrated vortex of similar diameter and had a larger radial gradient in circulation strength, compared to that of a stationary wing, for reduced frequency less than about 0.1. The axial-flow velocity was always wake-like, with its minimum value increasing with the reduced frequency. The peak value of the vorticity and the vortex strength and the lift-induced drag were higher during pitch-down than during pitch-up. The normalized circulation in the inner part of the axisymmetric vortex also exhibited a self-similar structure, which was insensitive to the reduced frequency. The induced drag increased with the reduced frequency.

关键词： Vortex Structure Freestream Velocity Turbulent Diffusion Laminar to Turbulent Transition Lift Coefficient Hysteresis NACA 0012 wing Configurations Wind Tunnel Tests rectangular wing

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Experimental and Numerical Analysis of a Streamwise Vortex Downstream of a Delta wing

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AIAA JOURNAL 2020年第7期58卷 2857-2868页

作者： Landa, Tim Klug, Lorenz Radespiel, Rolf Probst, Silvia Knopp, Tobias Tech Univ Carolo Wilhelmina Braunschweig Inst Fluid Mech Hermann Blenk Str 37 D-38108 Braunschweig Germany German Aerosp Ctr DLR Inst Aerodynam & Flow Technol Bunsenstr 10 D-37073 Gottingen Germany

The present paper analyzes the vortical flow downstream of a delta wing. The delta wing is designed to generate a vortex that resembles the vortex of a nacelle strake. The experimental results of stereoscopic particle image velocimetry measurements performed at different positions downstream of the delta wing display the streamwise development of the vortex. Details of the postprocessing of the measurement data and a quantification of the uncertainties are presented. The evaluation of the mean axial and tangential velocity components and Reynolds stresses provides insights to the vortex characteristics and their development in the streamwise direction. In addition, results of numerical simulations with the DLR TAU-code applying the Menter-Shear Stress Transport (SST) eddy viscosity model and the Speziale-Sarkar-Gatski/Launder-Reece-Rodi (SSG/LRR)-omega Reynolds stress model show the ability of the turbulence models to capture the vortex development. The experimental results indicate a preservation of the vortex strength and structure downstream of the delta wing. The Menter-SST model does not predict this preservation;rather it computes a rapid decay of vortex strength and an increase in vortex size. In contrast, the results of the SSG/LRR-omega model are in good agreement with the experiments concerning the mean flow development. However, both turbulence models underpredict the turbulence in the vortex core.

关键词： rectangular wing Delta wing Vortex Reynolds Averaged Navier Stokes Particle Image Velocimetry Aircraft Configurations Large Eddy Simulation Velocity Profiles Turbulence Models Numerical Analysis Shear Stress

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Frequency-domain optimal estimator for wing rock models

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1997年第4期20卷 748-753页

作者： Tan, SY Lan, CE UNIV KANSAS DEPT AEROSP ENGNLAWRENCEKS 66045

An estimation algorithm to identify the nonlinear aerodynamic model in wing rock from the free-to-roll test data is developed. This algorithm is based on an optimal estimation theory with a continuous cost function to minimize the difference between estimates and data. The optimality equations are reformulated in the frequency domain through Beecham-Titchener's averaging technique. The resulting equations are then solved by finite difference. A wing rock model of an 80-deg delta wing is used to verify the method. The method is then applied to a fuselage-vertical tail configuration in a free-to-roll test. The computed response based on the estimated aerodynamic model shows a fair agreement with measured data. Applications of this estimated aerodynamic model in control and aircraft design are discussed. In particular, the necessary additional damping for the suppression of limit-cycle oscillations can be computed. It is shown that unlike an 80-deg delta wing, roll angle feedback to increase the system stiffness can also suppress the body rock of a fuselage-vertical tail configuration.

关键词： Frequency Domain rectangular wing Fuselages Aircraft Design Critical Angle of Attack High Performance Aircraft Low Speed Wind Tunnel Sideslip Control Surfaces Optimal Control Theory

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SURFACE PRESSURE MEASUREMENTS ON A PITCHING SWEPT wing IN A WATER CHANNEL

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AIAA JOURNAL 1995年第10期33卷 1871-1879页

作者： PATTERSON, A RYMARZ, P RAMAPRIAN, BR WASHINGTON STATE UNIV DEPT MECH & MAT ENGNPULLMANWA 99164

This paper presents the results of surface pressure measurements on a swept wing of NACA 0015 profile and a back sweep angle of 15 deg, which was pitched at a uniform angular velocity. The pitching axis was perpendicular to the how direction so that the experiment simulated the pitch-up maneuver of a fixed-wing aircraft. The experiments were performed in an open-surface water channel. The object of the study was to understand the mechanics of vorticity production and dynamic stall in three-dimensional unsteady flows. The phase-locked pressure data which were obtained at several closely spaced spanwise locations of the wing were used to obtain information on the fluxes of spanwise and chordwise vorticity components, in addition to the usual information on the aerodynamic coefficients. The study showed that the three-dimensional dynamic stall over the slightly swept wing is less catastrophic and more gradual than the two-dimensional process over an unswept wing. Other important effects observed were a spanwise variation of the aerodynamic coefficients and the presence of spanwise periodicity in the production of vorticity following the onset of dynamic stall. The experimental data have been archived and are available to any interested user.

关键词： rectangular wing Aerodynamic Coefficients Unswept wings Two Dimensional Flow Pressure Coefficient Pitching Airfoil Fixed wing Aircraft Vortex Structure Lift Coefficient Aspect Ratio

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Effect of leading-edge form on performance of wing-movable tip strake configurations

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JOURNAL OF AIRCRAFT 2007年第5期44卷 1749-1753页

作者： Nikolic, Vojin R. Mankato State Univ Mankato MN 56001 USA

The effects of the leading edge form on the performance of a family of movable tip strakes in combination with a rectangular wing have been examined. Nine strake configurations that included four half-delta types, one modified half-delta having a portion of the leading edge curved, and four cdropped double delta or full double delta, were tested in a low-speed wing tunnel. Significant advantages were observed of the configurations employing strakes over the baseline wing. It was also observed that all strakes produced higher lift and drag coefficient than the clean wing. The highest lift-to-drag ratio was achieved when an 80/45 deg cropped double-delta strake was employed at moderate angle of attack, resulting in improvements of up to 26% over the clean wing.

关键词： Fuselages rectangular wing Vortex Strength Aerodynamic Efficiency Aeroplane Freestream Velocity Sweep Angle Flow Visualization Techniques MiG 29 Structural Weight

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Leading-Edge Vortex Structure over Multiple Revolutions of a Rotating wing

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JOURNAL OF AIRCRAFT 2013年第4期50卷 1312-1316页

作者： Venkata, Siddarth Kolluru Jones, Anya R. Univ Maryland Dept Aerosp Engn College Pk MD 20742 USA

The article aims to identify the formation, structure, and possible separation of the leading-edge vortex at the beginning of the wing stroke as well as after long convective times. To this end, flow visualization is performed for three wing revolutions to analyze the vortex structure and the location of the burst point. Dye flow visualization was performed at Reynolds numbers of 5000 or 10,000 using a mixture of 60% food coloring, 20% ethanol, and 20% milk. A stainless steel hypodermic needle was fixed along the chord of the upper surface of the wing at the wing root, injecting dye normal to the leading edge. To verify that the location of the dye injection point did not alter the vortex structure, the position of the needle was varied in both the chordwise and spanwise directions and was also mounted in the spanwise direction, injecting dye along the leading edge.

关键词： Vortex Structure rectangular wing wing Root Flow Visualization Lift Coefficient Aspect Ratio Aerodynamic Force Velocity Profiles Particle Image Velocimetry Six Degree of Freedom

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Identification of a Nonlinear wing Structure Using an Extended Modal Model

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JOURNAL OF AIRCRAFT 2009年第5期46卷 1614-1626页

作者： Platten, M. F. Wright, J. R. Cooper, J. E. Dimitriadis, G. Romax Technol Noise Vibrat & Harshness Team Nottingham NG7 2PZ England Univ Manchester Sch Mech Aerosp & Civil Engn Manchester M60 1QD Lancs England Univ Liverpool Dept Engn Liverpool L69 7ZE Merseyside England Univ Liege Dept Aerosp & Mech Engn B-4000 Liege Belgium

The nonlinear resonant decay method identifies a nonlinear dynamic system using a model based in linear modal space comprising the underlying linear system and a small number of additional terms that represent the nonlinear behavior. In this work, the method is applied to an aircraftlike wing/store/pylon experimental structure that consists of a rectangular wing with two stores suspended beneath it by means of nonlinear pylons with a nominally hardening characteristic in the store rotation degree of freedom. The nonlinear resonant decay method is applied to the system using multishaker excitation. The resulting identified mathematical model features five modes, two of which are strongly nonlinear, one is mildly nonlinear, and two are completely linear. The restoring force surfaces obtained from the mathematical model are in close agreement with those measured from the system. This experimental application of the nonlinear resonant decay method indicates that the method could be suitable for the identification of nonlinear models of aircraft in ground vibration testing.

关键词： Mathematical Models rectangular wing Finite Element Modeling Damping Ratio Aircraft Structures Frequency Response Functions Accelerometer Numerical Integration Data Acquisition System Aerospace Engineering

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Lateral Stability of High wing Configurations

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JOURNAL OF AIRCRAFT 2009年第6期46卷 2176-2178页

作者： Blake, William Gotwald, Carl Mayor, Michael Cunningham, Thomas USAF Res Lab Dept Aeronaut Wright Patterson AFB OH 45433 USA USAF Acad Dept Aeronaut Colorado Springs CO 80848 USA

The existing approximations for the effect of wing height on lateral stability are inadequate for configurations with a large ratio of body diameter to wing span. A wind-tunnel test was conducted at the US Air Force Academy Subsonic Wind Tunnel to determine that which approximation gives the correct trend for large diameter-to-span ratio. It is a closed circuit facility with a 3 × 3 ft test section. Five rectangular wings were tested with a root chord of 2 in. and spans corresponding to body diameter (d)/wing span (b) ratios of 0.2, 0.4, 0.6, 0.8, and 1. The results are linear for the smallest wing and largest wing with correlation coefficients R² in excess of 0.99. The smallest wing with d/b = 1 has more than double the lateral stability of the largest wing with d/b = 0.2. For a fixed body size, increase in d/b corresponds to decrease in wing span. The Mach 0.3 and 0.5 cases passed this test, whereas only the two largest wings exhibited the degree of correlation at Mach 0.15. The data show the peak value is reached for the smallest wing with d/b = 1.

关键词： Lateral Stability wing Configurations Aspect Ratio Airfoil Sections Sideslip Angle Wind Tunnel Tests Fuselages Supersonic Flow rectangular wing Angle of Attack

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ASYMPTOTIC THEORY OF BENDING-TORSION FLUTTER OF HIGH ASPECT RATIO wing IN THE TORSION CONTROLLED DOMAIN

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AIAA JOURNAL 1991年第5期29卷 780-781页

作者： KARPOUZIAN, G United States Naval Academy Annapolis Maryland 21402

AN asymptotic theory of bending-torsion flutter of a high aspect ratio wing with a unit-order bending-torsion stiffness ratio is developed. Two distinct (high and low) frequency domains are identified. For illustration, detailed analysis is carried out only in the high-frequency domain. The methodology is general and may be applicable to various wing configurations. To substantiate its adequacy, the classical case of a uniform unswept cantilever wing in an incompressible airflow is treated as a case study. The asymptotic results for flutter eigenvalues and mode shapes compare favorably with those obtained by a more exact treatment.

关键词： High Aspect Ratio Tapered wings Cantilever Frequency Domain Harmonic Oscillation Singular Perturbation Bernoulli Euler Beams Radius of Gyration rectangular wing wing Root

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VORTEX PANEL CALCULATION OF WAKE ROLLUP BEHIND A LARGE ASPECT RATIO wing

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AIAA JOURNAL 1986年第9期24卷 1417-1423页

作者： YEH, DT PLOTKIN, A UNIV MARYLAND DEPT AEROSP ENGNCOLLEGE PKMD 20742 SAN DIEGO STATE UNIV DEPT AEROSP ENGNSAN DIEGOCA 92182

A higher-order (linear vortex) panel method is used to calculate the three-dimensional wake rollup behind large aspect ratio symmetric wings in steady inviscid incompressible flow. Triangular-shaped panels are chosen to increase the geometric flexibility of the wake sheet. The wing spanwise circulation distribution is obtained from lifting-line theory, and the wake geometry is then evaluated in an iterative fashion by satisfying conservation of circulation, flow tangency, and zero-pressure jump for all wake panel surfaces in the near-wake region (two spans in length). The far wake is modeled by straight semi-infinite vortex filaments that are in the uniform stream direction. Numerical results are shown to compare favorably with those in the literature. The capability of the method to model a rectangular wing with a deflected flap is also studied. © 1986 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： High Aspect Ratio Vortex Filaments rectangular wing Freestream Velocity Incompressible Flow Kutta Condition Angle of Attack Low Aspect Ratio wings Shear Layers wing Geometry

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