Transonic time-response analysis of 3-degree-of-freedom conventionaland supercritical airfoils

Abstract

Aeroelastic time-response analyses are performed for two conventional airfoils, NACA 64A006 and NACA 64A010, and one supercritical airfoil, MBB A-3, in small-disturbance transonic flow. Response results for forces and displacements were obtained by simultaneousl y integrating the structural equations of motion with the unsteady aerodynamic forces computed using two transonic codes: LTRAN2-NLR and USTS. Three-degreesof-freedom—plunge, pitch, and aileron pitch—are considered. Flutter analyses are first performed, with the results used as a guideline for time-response parameter selection. Time-response results are presented showing that for each case the flight speed used to obtain neutrally stable responses is either exactly or nearly the same as the flutter speed determined in the separate flutter analysis. Effect of response amplitudes is investigated. Applicability and limitations of the two transonic codes are evaluated, compared, and discussed. Transonic time-response behavior of these airfoils is physically interpreted and discussed, and comparisons are made.