Comparison of Flight Loads, Derivatives and Gust Responses of a Transport Aircraft Using Panel Aerodynamics and CFD

Kurzfassung

This study compares flight loads, stability derivatives, and gust responses of a representative transport aircraft configuration as well as aerodynamic derivatives of an engine nacelle using panel aerodynamics (VLM/DLM) and computational fluid dynamics (CFD) in the subsonic regime. Results indicate that CFD solutions generally align with panel aerodynamics. In several parameters, however, discrepancies among VLM/DLM variants - specifically fuselage aerodynamic modeling via lifting surfaces versus slender-body assumptions - arise, and the corresponding CFD results often lie between the two solutions. This suggests that a typical fuselage effectively behaves as a hybrid of both potential flow variants. Control surface aerodynamic effectiveness show excellent agreement between CFD and panel aerodynamics for small deflections, and the CFD value decreases to approximately 0.8 at maximum travel. For the potential flow method, an aerodynamic modeling of the fuselage - either using lifting surface elements or slender body elements - is necessary, since its absence significantly influences the derivatives of control surfaces adjacent to the fuselage. For engine nacelles, their aerodynamic response represents a mixture of an ideal lifting-surface and an ideal slender body, similar to the fuselage. For the loads on the overall aircraft, the discrepancy between CFD and potential flow results only has a minor contribution to the wing's torsion moment due to the geometric position of the nacelle far in front of the wing's elastic axis. Although the potential flow solution predicts a higher lift slope for the nacelle compared to CFD, this effect is compensated by the shorter lever arm relative to the elastic axis.