Wake Modelling with Embedded Lateral and Directional Stability Sensitivity Analysis for Aerial Refuelling or Formation Flight

摘要

Air-to-air refuelling and formation flight are two operational practises that can result in fuel savings. However, aircraft flying in close proximity can experience disturbances in terms of aerodynamic forces and moments due to wake turbulence, downwash, and aerodynamic coupling between aircraft. In order to predict the effect of an aircraft wake on the lateral and directional stability of a trailing aircraft, a coupled vortex lattice method was developed and combined with sensitivity analysis that uses an adjoint-based method to quickly predict the change in rolling moment and yawing moment caused by changes in the relative vertical and lateral position between the two aircraft. A combination of wind-tunnel and flight test data were used as test cases to validate the aerodynamic prediction model and adjoint derived sensitivities. Results showed good agreement with existing data. Regions of static stability were found using the adjoint based sensitivity analysis. These areas of stability were limited to areas where the lateral offset between aircraft was no greater than 40 % of the wingspan. The adjoint-based sensitivities were shown to be accurate when compared to a finite-difference based approach, but were calculated approximately four times faster.