Assessment of T-tail flutter using an enhanced potential flow theory approach and linearized frequency domain CFD data

Abstract

This paper aims at assessing the gain in accuracy for T-tail flutter point prediction obtained by a strip theory approach used to enhance common linear potential flow theory based unsteady aerodynamic forces. The common approach neglects unsteady aerodynamic forces induced by lifting surface inplane and roll motion, which are crucial for T-tail flutter. The strip theory approach computes these additional terms based on aerodynamic forces from a steady state reference condition and the modal data of the underlying structural model. The correction is done by superposing the additional terms with the aerodynamic forces from the standard procedure. Generalized aerodynamic forces produced by the common approach and the enhanced approach in addition to resulting flutter points and aerodynamic Modal Power Transfer matrices are compared to those computed with aerodynamic forces from the linearized frequency domain CFD solver TAU-LFD. Two Mach numbers of 0.4 and 0.69 are chosen for this assessment. The model for the study is a generic T-tail with unswept and non-tapered vertical and horizontal tail planes. Significant improvements of the flutter points of the T-tail for both Mach numbers can be achieved by the enhancement in relation to the CFD approach. A comparison of generalized aerodynamic forces and aerodynamic Modal Power Transfer values, however, reveals strengths and weaknesses of the method