Aerodynamic Interference of a Large and a Small Aircraft.

Karkehabadi, Reza

doi:10.2514/1.4570

Cited by 12 publications

(3 citation statements)

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“…Furthermore, they are indispensable in the investigation of interference problems, such as when the wake encounters a second lifting surface, which is likely to happen in HALE vehicles between wing and tail. Vortices incident upon bodies can give rise to substantial unsteady loading 31 , and the aerodynamic loads of a trailing wing can be affected by the wake of the leading wing even at a 10-chord distance 32 . Note finally that linearized methods in which a flat wake is assumed, such as the Doublet-Lattice Method 33,34 , are not suitable for these problems.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Nonlinear Flexible Aircraft Dynamics Including Free-Wake Effects

Murua

Palacios

Graham

2010

AIAA Atmospheric Flight Mechanics Conference

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This paper addresses the unified aeroelastic and flight dynamics characterization of lowspeed slender-wing aircraft, including free-wake effects and aerodynamic interference. An analysis framework is presented that targets the prediction of stability and handling qualities of high-altitude long-endurance vehicles, which are prone to experience large wing excursions, leading to an inherently nonlinear and coupled problem between aerodynamics, elasticity and flight dynamics. In this work, the structural dynamics are based on a geometrically-exact composite beam model, discretized using displacement-based finite elements, and cast into an extended flexible-body dynamics model. The aerodynamic model is defined by a general unsteady vortex lattice method. The governing equations of motion of the integrated system are formulated in a tightly-coupled state-space form, which allows for the equations to be solved simultaneously. Verification of the model has been carried out for static and dynamic problems, including both rigid and flexible wings. Numerical studies are presented for the particular case of prescribed rigid-body motions, paying special attention to the likely interference between wake and tail. Results show that the current approach represents a suitable alternative for configuration analysis of flexible atmospheric vehicles, offering a good balance between degree of fidelity and computational cost. Nomenclature a = body-attached (global) reference frame p Δ = pressure jump across aerodynamic panel * , kl kl a a = aerodynamic influence coefficients R = beam local position vector B = deformed (local) reference frame s = arc length along reference line b = undeformed (local) reference frame t = physical time b Δ = spanwise dimension of aerodynamic panel V = beam local translational velocity Ba C = coordinate transformation matrix from a to B V ∞ = free-stream velocity c Δ = chordwise dimension of aerodynamic panel v = translational velocity of the a frame G = inertial (ground) frame of reference k v = downwash b w K ,K = number of bound and wake vortex-rings considered w = normal component of the non-vortical induced velocity K ,k = current and initial beam local curvatures X = coordinates on aerodynamic lattice p = position of the a frame with respect to G x = state vector Greek letters Γ = circulation strength Ω = beam local angular velocity γ = beam local force strain ω = angular velocity of the a frame ζ = quaternions Ψ = Cartesian Rotation Vector κ = beam local moment strain 2 Subscripts A = aerodynamic R = rigid-body b = bound, corresponding to lifting surface S = structural , , i j k = chordwise, spanwise and total panel counters w = wake Superscripts * • = corresponding to wake • = cross-product operator • = derivatives with time, t • = vector magnitude ′ • = derivatives with the curvilinear coordinate, s

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Section: Introductionmentioning

confidence: 99%

Modeling of Nonlinear Flexible Aircraft Dynamics Including Free-Wake Effects

Murua

Palacios

Graham

2010

AIAA Atmospheric Flight Mechanics Conference

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“…The development of the first steady VLM dates back to work done by Hedman in the 1960s [6], with unsteady modifications introduced by Thrasher et al [7] and Konstadinopoulos et al [8] in the 1970s and 80s. However, the VLM, with various modifications and enhancements, is used even today for low-order modeling and engineering applications, with recent examples ranging from flight dynamics analysis [9,10], analysis of yacht sails [11], calculation of aerodynamic interference effects [12][13][14], post-stall analysis [15,16], flapping-wing analysis [17][18][19][20], wind turbines [21,22], design optimization [19,23,24] and aeroelasticity [25][26][27]. Modified VLMs have also been extensively used for modeling steady and unsteady flows past delta-wings [28], propeller aerodynamics [29], propeller-wing interactions [30], ground effect and formation flight [31][32][33][34], compressibility effects and transonic flow over wings [35,36], system identification [37], and for rapid performance prediction in adaptive control of aircraft [38,39].…”

Section: Introductionmentioning

confidence: 99%

A Low-Order Method for Prediction of Separation and Stall on Unswept Wings

Hosangadi¹,

Gopalarathnam²

2020

Preprint

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A low-order method is presented for aerodynamic prediction of wings operating at nearstall and post-stall flight conditions. The method is intended for use in design, modeling, and simulation. In this method, the flow separation due to stall is modeled in a vortex-lattice framework as an effective reduction in the camber, or "decambering." For each section of the wing, a parabolic decambering flap, hinged at the separation location of the section, is calculated through iteration to ensure that the lift and moment coefficients of the section match with the values from the two-dimensional viscous input curves for the effective angle of attack of the section. As an improvement from earlier low-order methods, this method also predicts the separation pattern on the wing. Results from the method, presented for unswept wings having various airfoils, aspect ratios, taper ratios, and small, quasi-steady roll rates, are shown to agree well with experimental results in the literature, and computational solutions obtained as part of the current work.

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“…Hence, while the DLM has dominated in fixed-wing aircraft aeroelasticity, the UVLM has been gaining ground in situations where free-wake methods become a necessity because of geometric complexity, such as flapping-wing kinematics [69][70][71], rotorcraft [72,73], or wind turbines [74][75][76][77][78][79][80]. With the advent of novel vehicle configurations and increased structural flexibility for which the underlying assumptions of the DLM no longer hold, the UVLM constitutes an attractive solution for aircraft dynamics problems and has been recently exercised in problems such as unsteady interference [53,81], computation of stability derivatives [82], flutter suppression [83], gust response [8,84], optimisation [85], morphing vehicles [86], and coupled aeroelasticity and flight dynamics [18].…”

mentioning

confidence: 99%