The influence of an additional degree of freedom on subsonic wing rock of slender delta wings

Elzebda, Jamal M.; Mook, Dean T.; Nayfeh, Ali H.

doi:10.2514/6.1987-496

Cited by 6 publications

(2 citation statements)

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“…It seems reasonable to study this phenomenon by an example of simple lifting surfaces, such as delta wings. Self-induced oscillations of such wings were studied experimentally in [1][2][3][4], and numerical simulations of this phenomenon were performed in [5][6][7][8]. The present paper reports the results of a numerical study of self-induced wing rock of a delta wing, in particular, in the presence of external disturbances.…”

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confidence: 98%

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Numerical study of self-induced wing rock of a low-aspect-ratio delta wing in the presence of external disturbances

Shumsky

2010

J Appl Mech Tech Phy

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Self-induced wing rock of a delta wing, in particular, in the presence of external disturbances are studied by means of numerical simulations of a separated flow of an ideal incompressible fluid around a delta wing. The results obtained are compared with experimental data. The vortex nature and the mechanism of self-induced oscillations are studied. Regions of synchronization of the aerodynamic self-oscillatory system in the presence of external disturbances are identified. Methods of suppression of self-induced wing rock are proposed.Key words: numerical study, delta wing, self-induced wing rock, external disturbances, capture of frequency, suppression of self-induced oscillations.Separated flows at high angles of attack can include undesirable self-induced roll-oscillations of flying vehicles. It is known that such oscillations can precede the regime of the flying vehicle going into a spin. In this case, there occur self-induced oscillations owing to flow separation from the leading edges of the lifting surfaces. It seems reasonable to study this phenomenon by an example of simple lifting surfaces, such as delta wings. Self-induced oscillations of such wings were studied experimentally in [1][2][3][4], and numerical simulations of this phenomenon were performed in [5][6][7][8]. The present paper reports the results of a numerical study of self-induced wing rock of a delta wing, in particular, in the presence of external disturbances.1. A mathematical model of unsteady motion of a slender delta wing in an ideal incompressible fluid is considered. The following assumptions of the nonlinear theory of the wing in a separated ideal fluid flow are used: the flow outside the wing and the vortex wake is potential; the separation line on the sharp edges is fixed; there are no secondary separations; the no-slip conditions on the wing, the Joukowski postulate on the edges, the kinematic and dynamic conditions on the vortex sheet, and the condition of decaying disturbances at infinity are satisfied.The wing motion is assumed to start moving from the state at rest with a constant velocity V . At the time t 0 , the wing with a stable vortex structure formed above acquires a degree of freedom in terms of rolling. The rotation axis is aligned along the root chord of the wing (Fig. 1). Beginning from the time t 0 , the equations of unsteady aerodynamics are solved together with the equation of wing motion in terms of its rollingwith the initial conditions (initial deviations in terms of rolling at the time τ 0 )In Eqs. (1) and (2), γ is the rolling angle, α is the angle of attack, τ = tV /b is the dimensionless time, t is the time, b is the length of the root chord, λ is the aspect ratio, m x = 2M x /(ρV 2 Sl), c 1 = ρb 2 Sl/(2I x ), M x is the rolling moment, ρ is the fluid density, and I x , S, and l are the moment of inertia, the wing area, and the wing span, respectively.

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confidence: 98%

“…The algorithm of the numerical solution of the nonlinear problem of the separated unsteady flow around a delta wing is constructed on the basis of the method of discrete vortices [5][6][7][8]. A rectangular vortex cascade (the same as that in [7]) was used in the calculations.…”

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confidence: 99%