Aeroelastic Stability and Response of Composite Swept Wings in Subsonic Flow Using Indicial Aerodynamics

Abstract

In this study, the aeroelastic stability and response of an aircraft swept composite wing in subsonic compressible flow are investigated. The composite wing was modeled as an anisotropic thin-walled composite beam with the circumferentially asymmetric stiffness structural configuration to establish proper coupling between bending and torsion. Also, the structural model consists of a number of nonclassical effects, such as transverse shear, material anisotropy, warping inhibition, nonuniform torsional model, and rotary inertia. The finite state form of the unsteady aerodynamic loads have been modeled based on the indicial aerodynamic theory and strip theory in the subsonic compressible flow. Novel Mach dependent exponential approximations of the indicial aerodynamic functions have been developed. The extended Galerkin’s method was used to construct the mass, stiffness, and damping matrices of the nonconservative aeroelastic system. Eigen analysis of the system was performed to obtain the aeroelastic instability (divergence and flutter) boundaries. Also, solving the equations of motion in the time domain leads to the aeroelastic response of wing in different flight speeds. The obtained results are compared with the available results in the literature, which reveals an excellent agreement. The numerical results obtained in this article seek to clarify the effects of geometrical and material couplings and flight Mach number on the aeroelastic instability and response of composite wings in subsonic compressible flow.

Nonlinear aeroelastic analysis of high-aspect-ratio wings using indicial aerodynamics

“…It can be seen from Table 8 the difference between the flutter speeds obtained from both cases increases as the flight altitude increases. Note that the apparent mass effects have been neglected in the compressible case due to the fact that any concept of apparent mass is meaningless in this flight speed regime [18,22,40]. Moreover, the linear flutter boundary is obtained through an iterative process using the appropriate indicial aerodynamics.…”

“…For a finite-span wing, the modified strip theory as well as the modified lift curve slope can be used to extend the 2D aerodynamics to the 3D case. The modified strip theory has been extensively used in preliminary design due to rapid modeling and high computational efficiency [21,40,41]. Assuming that the lift coefficient on each chordwise strip of the wing is proportional to the local angle of incidence a y ð Þ and that the lift on one strip has no influence upon another, the total lift acting on a single wing can be found as…”

“…(1) and also slope of the lift curve, it is possible to add the effect of sweep angle to analyses such that unsteady aerodynamic loads can be determined for a swept wing based on the indicial functions in subsonic regime. References [21,40] provide more details.…”

“…Finally, it should be mentioned that in contrast to the compressible aerodynamics, in which any concept of virtual mass is meaningless [19,22,40], the non-circulatory contributions of lift and moment are needed to be taken into account in the incompressible flow. Hence, to describe the unsteady aerodynamic loads in incompressible flight speed regime, the following aerodynamic non-circulatory components should be added to the circulatory parts expressed by Eqs.…”

Classical flutter analysis of composite wind turbine blades including compressibility

“…Aerodynamic loads with respect to the coordinate system at a distance b(a+1) aft of the leading edge (Theodorsen's coordinate) are defined in terms of the indicial functions as 19,27 L c ae z, t…”