Aeroelastic Response Analysis of Two Dimensional, Single and Two Degree of Freedom Airfoils in Low-Frequency, Small-Disturbance Unsteady Transonic Flow.

摘要

A procedure is developed to obtain the aeroelastic responses of single and two degree of freedom aeroelastic systems in transonic flow. The fluid is described by the two dimensional unsteady low-frequency transonic potential equation based on small disturbance theory. The aerodynamic computer code LTRAN2 which is based on a fully implicit time integration scheme is employed to obtain the aerodynamic forces. The structural equations are simultaneously integrated with the potential flow equations by a numerical method and the aeroelastic responses are obtained. Results for neutrally stable responses are compared with those obtained by the U-g method. Aeroelastic responses are obtained for flat plates (single and two degree of freedom) at M = 0.7 by the linear part of LTRAN2. Examples of an NACA 64A006 airfoil at Mach numbers of 0.88 and 0.85 are also analyzed. Response results obtained for a single pitching degree of freedom system at M = 0.88 are compared with an existing solution. The response results obtained for a two degree of freedom system at M = 0.85 for neutrally stable condition are correlated with those obtained by the flutter analysis. Results also include stable and unstable response curves and their variations with altitude. (Author)