Potential Panel and Time-Marching Free-Wake-Coupling Analysis for Helicopter Rotor

Wie, Seong Yong; Lee, Seongkyu; Lee, Duck Joo

doi:10.2514/1.40001

Cited by 38 publications

(25 citation statements)

References 13 publications

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“…However, the simplest remedy is to introduce a vortex-core to model the inner viscous part of the vortex filament. Several models have been proposed 35,39,45 , but in all of them the choice of core size lacks theoretical or physical justification. As a consequence, it has to be defined cautiously, since it can have a significant influence on the solution.…”

Section: Introductionmentioning

confidence: 99%

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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%

“…Blade-Vortex Interaction (BVI) has been widely investigated in the rotorcraft community [35][36][37][38][39] . The same physics are also observed when wake-dynamics are studied in order to determine safe take-off and landing distances, since the wake of a leading aircraft may affect a following one.…”

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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“…In order to improve the accuracy and/or stability of the wake rollup, other higher-order schemes have been proposed in the literature, such as a two-step Euler 15 and the fourth order AdamsBashforth-Moulton. 16 In this work it will be approximated as…”

Section: Aerodynamic Model: Unsteady Vortex Lattice Methodsmentioning

confidence: 99%

Stability and Open-Loop Dynamics of Very Flexible Aircraft Including Free-Wake Effects

Murua

Hesse

Palacios

et al. 2011

52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

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The paper investigates the coupled aeroelasticity and flight mechanics of very flexible lightweight aircraft. A geometrically-exact composite beam formulation is used to model the non-linear flexible-body dynamics, including rigid-body motions. The aerodynamics are modeled by a general 3-D unsteady vortex-lattice method, which can capture the instantaneous shape of the lifting surfaces and the free wake, including large displacements and interference effects. The coupled governing equations are solved in a variety of ways, including linear and non-linear time-domain simulations of the full vehicle and frequencydomain linear stability analysis around trimmed configurations. The resulting framework for the Simulation of High-Aspect Ratio Planes (SHARP) provides a mid-fidelity representation of flexible aircraft dynamics, based on an intuitive and easily linearizable structural representation based on displacements and the Cartesian rotation vector, time-domain 3-D aerodynamics, and at relatively low computational costs. Previous verification studies on the structural dynamics and aerodynamics modules are complemented here with studies on the flexible-body implementation and on the integrated simulation methodology. A numerical investigation is finally presented on a representative high-altitude long-endurance model aircraft, investigating its stability properties and its open-loop dynamic response.

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“…If a prescribed wake were to be considered, the integral term would be dropped, but for a fully force-free wake it is necessary to retain it and time-integration is required to determine the location of the rolled-up wake. Conventionally, this is done using an explicit one-step Euler method, but in order to improve the accuracy and/or stability of the wake roll-up other higher-order schemes have been also proposed in the literature, such as a two-step Euler [165] and the fourth-order Adams-Bashforth-Moulton [73].…”

Section: General Nonlinear Formulationmentioning

confidence: 99%

“…The DLM offers a faster way of computing unsteady aerodynamic loads, but it is a linear method restricted to small out-ofplane harmonic motions with a flat wake. 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%