Aeroelastic analysis of high aspect ratio wing in subsonic flow

Abstract

High altitude long endurance (HALE) UAVs have very flexible wing because of mission requirements. High lifts to drag ratio and more surveillance time in air requirements make their structure highly flexible and large tip deflections can occur which can be as large as 30% of wing semi span. Linear theory fails to accurately analyze such deformation and the changes in the structural and aerodynamic characteristics of the wing accompanying such deformation. Low aspect ratio wing and stiff structures can be best simulated by normal modes in aeroelastic analysis. However high aspect ratio restricts the use of reduce order model based on linear normal modes in aeroelastic analysis. The reason not to use the linear elastic normal modes in high AR wings is the stiffening effects because of large deflections. These effects cause the normal modes to fail as a good basis set. In such situation one needs to use the modified basis function. The computational model used in this work consists of a modified modal based reduced order nonlinear structural dynamics model coupled to a ZONA6's lifting surface method which is a higher-order panel method. Using modified modal basis, geometrical nonlinearities has been captured very well. Aeroelastic analyses agree well with the published data.