A Computational Study of a Canonical Pitch-Up, Pitch-Down Wing Maneuver

Eldredge, Jeff D.; Wang, Chengjie; Ol, Michael V.

doi:10.2514/6.2009-3687

Cited by 122 publications

(84 citation statements)

References 6 publications

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“…Hence, there will be no need to solve an algebraic system of equations to determine the bound circulation as usually done in the implementation of discrete vortex models such as the unsteady vortex lattice method. The developed model is applied to some canonical pitch motions such as the ones introduced by Eldredge et al [7]. The obtained results are then validated against the numerical and experimental results of Ramesh et al [23].…”

Section: Introductionmentioning

confidence: 93%

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Geometrically-exact unsteady model for airfoils undergoing large amplitude maneuvers

Yan

Taha

Hajj

2014

Aerospace Science and Technology

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A semi-analytical, geometrically-exact, unsteady potential flow model is developed for airfoils undergoing large amplitude maneuvers. For this objective, the classical unsteady theory of Theodorsen is revisited relaxing some of the major assumptions such as (1) flat wake, (2) small angle of attack, (3) small disturbances to the mean flow components, and (4) time-invariant free-stream. The kinematics of the wake vortices is simulated numerically while the wake and bound circulation distribution and, consequently, the associated pressure distribution are determined analytically. The steady and unsteady behaviors of the developed model are validated against experimental and computational results. The model is then used to determine the lift frequency response at different mean angles of attack. Both qualitative and quantitative discrepancies are found between the obtained frequency response and that of Theodorsen at high angles of attack.

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Section: Introductionmentioning

confidence: 93%

“…They solved the two-dimensional Navier-Stokes equations on a flat plate undergoing large amplitude canonical pitch maneuvers that are presented in Ref. [7] and shown here in Fig. 8.…”

Section: Unsteady Behaviormentioning

confidence: 99%

Geometrically-exact unsteady model for airfoils undergoing large amplitude maneuvers

Yan

Taha

Hajj

2014

Aerospace Science and Technology

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“…Both these motions are generated with a modified version of the Eldredge function which produces a ramp motion with smoothed corner [20,31] maneuvers. The pitch histories are given by:…”

Section: Definition Of Motion Kinematicsmentioning

confidence: 99%

Leading-edge flow criticality as a governing factor in leading-edge vortex initiation in unsteady airfoil flows

Ramesh

Granlund

et al. 2017

Theor. Comput. Fluid Dyn.

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A leading-edge suction parameter (LESP) that is derived from potential flow theory as a measure of suction at the airfoil leading edge is used to study initiation of leading-edge vortex (LEV) formation in this article. The LESP hypothesis is presented, which states that LEV formation in unsteady flows for specified airfoil shape and Reynolds number occurs at a critical constant value of LESP, regardless of motion kinematics. This hypothesis is tested and validated against a large set of data from CFD and experimental studies of flows with LEV formation. The hypothesis is seen to hold except in cases with slow-rate kinematics which evince significant trailing-edge separation (which refers here to separation leading to reversed flow on the aft portion of the upper surface), thereby establishing the envelope of validity. The implication is that the critical LESP value for an airfoil-Reynolds number combination may be calibrated using CFD or experiment for just one motion and then employed to predict LEV initiation for any other (fast-rate) motion. It is also shown that the LESP concept may be used in an inverse mode to generate motion kinematics that would either prevent LEV formation or trigger the same as per aerodynamic requirements.

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“…However, the time required for the brushed DC motor used in the experiment to realize the transition of the wing in water is not clear. In order to quantify the acceleration in transitions, we use a continuously differentiable C ∞ function [Eldredge et al, 2009] to replace the ideal pitching motion, as shown in figure 13. The new function is given by…”

Section: Sweeping-pitching Platementioning

confidence: 99%

A predictive quasi-steady model of aerodynamic loads on flapping wings

Goosen

Keulen

2016

J. Fluid Mech.

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Quasi-steady aerodynamic models play an important role in evaluating aerodynamic performance and conducting design and optimization of flapping wings. The kinematics of flapping wings is generally a resultant motion of wing translation (yaw) and rotation (pitch and roll). Most quasisteady models are aimed at predicting the lift and thrust generation of flapping wings with prescribed kinematics. Nevertheless, it is insufficient to limit flapping wings to prescribed kinematics only since passive pitching motion is widely observed in natural flapping flights and preferred for the wing design of flapping wing micro air vehicles (FWMAVs). In addition to the aerodynamic forces, an accurate estimation of the aerodynamic torque about the pitching axis is required to study the passive pitching motion of flapping flights. The unsteadiness arising from the wing's rotation complicates the estimation of the centre of pressure (CP) and the aerodynamic torque within the context of quasisteady analysis. Although there are a few attempts in literature to model the torque analytically, the involved problems are still not completely solved. In this work, we present an analytical quasi-steady model by including four aerodynamic loading terms. The loads result from the wing's translation, rotation, their coupling as well as the added-mass effect. The necessity of including all the four terms in a quasi-steady model in order to predict both the aerodynamic force and torque is demonstrated. Validations indicate a good accuracy of predicting the CP, the aerodynamic loads and the passive pitching motion for various Reynolds numbers. Moreover, compared to the existing quasi-steady models, the presented model does not rely on any empirical parameters and, thus, is more predictive, which enables application to the shape and kinematics optimization of flapping wings.

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A Computational Study of a Canonical Pitch-Up, Pitch-Down Wing Maneuver

Cited by 122 publications

References 6 publications

Geometrically-exact unsteady model for airfoils undergoing large amplitude maneuvers

Geometrically-exact unsteady model for airfoils undergoing large amplitude maneuvers

Leading-edge flow criticality as a governing factor in leading-edge vortex initiation in unsteady airfoil flows

A predictive quasi-steady model of aerodynamic loads on flapping wings

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