Aerodynamics of Civil Transport Supersonic Aircraft Numerical and experimental investigations of the low-speed aerodynamics of Supersonic Commercial Transport aircraft
The EC project EPISTLE, European Project for Improvement of Supersonic Transport Low-speed Efficiency, launched in year 2000, focused on the low-speed aerodynamic characteristics of the European Supersonic Commercial Transport (ESCT) aircraft. Beyond the objective of improving the low-speed performance of the ESCT by means of deflectable leading edge flaps devices, the EPISTLE project intended to assess the capability of numerical methods to predict the complex, vortex-dominated flows developing on the high leading edge sweep wing of a supersonic aircraft operated in high lift conditions and to validate design methodologies based on these numerical methods.
Onera contributed to the different numerical and experimental studies of EPISTLE. The elsA CFD software in association with the far-field drag post-processor developed at Onera have been applied to evaluate the low-speed aerodynamic characteristics of different leading edge flap configurations. In the first stage of the project, this numerical methodology has been validated on the EUROSUP low-speed configuration using the enhanced experimental database acquired during the EPISTLE tests in the DNW-HST wind tunnel. A numerical investigation of the sensitivity to the leading edge flaps deflections has then been carried out using these validated numerical methods.
In the design task of EPISTLE, Onera performed constrained numerical optimisations of the leading edge devices geometry and deflections. An automated optimisation loop has been developed for this purpose, which embeds a mesh deformation technique, the elsA software used to solve the Euler equations, the far-field drag extraction technique and a dedicated aerodynamic constraints module. Two leading edge flap configurations, designed in EPISTLE were down-selected by the partners for being verified during a wind tunnel test campaign.
Automated aerodynamic simulation software
used for leading edge flap design optimisation
EPISTLE model in the Onera F1 wind tunnel
The wind tunnel tests conducted by Onera in its large pressurized low-speed wind tunnel F1 has been an important step of these research activities. Te performance improvements, over the reference EUROSUP configuration, achieved by the EPISTLE designs were confirmed to be in close agreement with the numerical predictions, validating the design methodologies developed in EPISTLE and proving that important low-speed performance gains can be achieved with carefully designed low-speed devices. These tests also provided a unique experimental database for Reynolds numbers up to 22 millions including detailed vortex flow development investigations based on wake plane surveys and boundary layers traverses measurements.
>Surface pressure distribution - CFD results (elsA solver).
Total pressure losses illustrating vortex flow in the wake
CFD results with the elsA solver
Finally, Onera has contributed to the analysis of the experimental database by means of RANS calculations of one of the EPISTLE configurations in the conditions of F1 tests. A specific focus has been the vortex flow development. The effects of the F1 wind tunnel walls were also investigated numerically through additional RANS calculations using the Chimera grids technique.
The numerical and experimental studies conducted in EPISTLE improved the understanding of the vortex flow developing on a supersonic aircraft wing in low-speed conditions and helped to prepare the methods and tools needed for the design of the low-speed flaps devices of any future supersonic aircraft.
Numerical investigation of F1 wind tunnel walls effects
by means of RANS calculation using the Chimera grids technique
