Reduction of Wave & Lift-Dependent Drag for Supersonic Transport Aircraft
The strategic objective of the EUROSUP project was to contribute to the improvement of the competitive position of Europe as a partner in a potential future supersonic transport aircraft programme. The aim of the project was to demonstrate and assess the application of advanced aerodynamic technology to a representative second-generation supersonic transport configuration. In particular, means of reducing the drag due to shock waves and lift were investigated. Challenging target values for lift / drag (L/D) for three aircraft design points, over-sea cruise (M = 2.0, L/D>10), over-land cruise (M = 0.95, L/D>15) and take-off climb out / landing approach (L/D>8), were achieved. These targets for aerodynamic performance represent improvements of between 20% and 30% relative to the performance of first generation supersonic transport aircraft. Thus the research project is a very significant first step towards a second-generation supersonic transport that would be economically viable and environmentally acceptable. Four major activities were completed in the project: -CFD methods were evaluated for the aerodynamic analysis and design of a supersonic transport configuration through comparison with experimental data for drag. -Aerodynamic design methods were evaluated for the optimisation of variants of a single wing shape to meet the three design points. -A wind-tunnel model incorporating the aerodynamic designs was manufactured and tested at supersonic, transonic, and take-off and landing conditions. -The aircraft model and flight vehicle configurations were analysed using CFD methods, and the results compared with the design predictions and wind-tunnel model measurements. It was concluded that: -The initial evaluation of CFD tools showed good prediction accuracy for supersonic cruise, moderate accuracy for transonic cruise but relatively poor accuracy for low speed. -The application of aerodynamic design tools at high speed showed good performance by a linear theory method for supersonic design. The direct optimisation Euler methods produced a dual-point transonic/supersonic wing design that met the L/D targets. A large increment in transonic L/D was obtained, without compromising the supersonic L/D, by optimising the deflection angles for high-lift devices. The role for inverse design methods in SCT wing design was unclear. The limited evaluation showed no gains from application to wing LE profile shaping. At low speed a semi-empirical design procedure produced a wing design that met the L/D target, however there was poor modelling of the flow physics and no appreciation of design sensitivities could be obtained. -The aerodynamic performance predicted in design was confirmed by wind-tunnel model tests at subsonic, transonic and supersonic speeds, and by independent CFD analyses. The CFD analyses gave very good agreement with the wind-tunnel results. Predictions of the increments in aerodynamic performance due to scale effect and the geometric change from model to full-scale aircraft showed that the target values for L/D would be achieved. -No satisfactory computational procedure was found for low-speed design. Further research was therefore recommended to investigate the low-speed flows and define a design method.