State-space inflow models for rotor aeroelasticity

Peters, David A.; Karunamoorthy, Swami

doi:10.2514/6.1994-1920

Cited by 10 publications

(9 citation statements)

References 7 publications

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“…(19) is consistent with the fact that the non-circulatory force is the force required to accelerate a mass of air cylinder of radius b with the acceleration of the mid-chord point. However, it should be noted that the acceleration term between the brackets is not the inertial acceleration of the mid-chord point (i.e., not the acceleration with respect to the still fluid), but rather the time rate of change of the velocity of the mid-chord point with respect to the body axes.…”

Section: Non-circulatory Contributionssupporting

confidence: 69%

“…As for the aerodynamic loads, the non-circulatory contributions are given directly in Eq. (19). After determining the positions and the velocities of the wake vortices, the circulatory loads induced by each wake vortex can be determined from Eqs.…”

Section: Numerical Implementationmentioning

confidence: 99%

“…Most of the finite-state models are obtained by approximating the curves of either the Wagner function in the time-domain, or the Theodorsen function in the frequency-domain (e.g., see the efforts of Garrick [9], Jones [12], Jones [13], and Vepa [33]). In contrast to these approximations, there are finite-state models that were developed from the basic principles (e.g., Peters and Karunamoorthy [18,19], Peters et al [20], and Peters [17]). Table 1 shows a taxonomy of the unsteady flow regimes and the applicability of the above referenced models.…”

Section: Introductionmentioning

confidence: 99%

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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: Non-circulatory Contributionssupporting

confidence: 69%

Section: Numerical Implementationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…For forward flights with a low reduced frequency k, typically k < 0.1, the quasi-steady aerodynamics is applicable. For forward flight with a relatively high k with local angles of attack up to 25 • , a number of aerodynamic theories can be applied to capture the unsteadiness with a good accuracy either for twodimensional or three-dimensional wings, e.g., Theodorsen [51], Shwarz and Sohngen (see [9]), Peters et al [39,34,36,35,37,38], Jones [24][25][26], and Reissner [41]. In addition, methodologies such as the unsteady lifting line theory, the unsteady vortex lattice method, and the unsteady doublet lattice method can also be used to capture the unsteady effects on three-dimensional wings.…”

Section: Aspect Ratio Cmentioning

confidence: 99%

State-space representation of the unsteady aerodynamics of flapping flight

Taha

Hajj

Beran

2014

Aerospace Science and Technology

137

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A state-space formulation for the aerodynamics of flapping flight is presented. The Duhamel's principle, applied in linear unsteady flows, is extended to non-conventional lift curves to capture the LEV contribution. The aspect ratio effects on the empirical formulae used to predict the static lift due to a stabilized Leading Edge Vortex (LEV) are provided. The unsteady lift due to arbitrary wing motion is generated using the static lift curve. Then, state-space representation for the unsteady lift is derived. The proposed model is validated through a comparison with direct numerical simulations of Navier-Stokes on hovering insects. A comparison with quasi-steady models that capture the LEV contribution is also performed to assess the role of unsteadiness. Similarly, a comparison with classical unsteady approaches is presented to assess the LEV dominance. Finally, a reduced-order model that is more suitable for flight dynamics and control analyses is derived from the full model.

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“…impulse function l downwash due to g w ¼ Àu w l n coefficients of velocity due to shed wake v downwash due to bound vorticity, ¼ Àu b v n components of velocity due to bound vorticity x dummy variable of integration r density of air, kg/m 3 t nondimensional time in Karunamoorthy (1993, 1994), t t t n pressure expansion coefficients f,Z elliptical coordinates F nondimensional pressure, p/rV 2 F A acceleration potential F n expansion functions for F F V velocity gradient potential C velocity potential o frequency, rad/s ( ) L lower surface, lim y!0 À À1oxo þ 1 ( ) U upper surface, lim y!0 þ À1oxo þ 1 ð Á Þ q( )/qt rotary-wing researchers, in trying to accommodate the need for general motion theories in rotorcraft, have used the Wagner function in a convolution integral (Beddoes, 1983), thus ignoring the returning wake.…”

Section: Article In Pressmentioning

confidence: 99%