In order to make substantial progress in reducing the environmental impact of aircraft, a key technology is the reduction of aircraft weight. This challenge requires the development and the assessment of new technologies and methodologies of load prediction and control. To achieve the investigation of the specific case of gust load, ONERA defined a dedicated research program based on both wind tunnel test campaigns and high fidelity simulations.To reach the experimental objectives, a set-up was designed, manufactured and implemented within the ONERA S3Ch transonic wind tunnel facility. The first component, called gust generator, consists of two oscillating airfoils installed upstream of the wind tunnel test section and allows to produce air flow deflections. The second component, the test model, is a two degrees-of-freedom aeroelastic model of a supercritical airfoil. A test campaign has been performed leading to the generation of databases for high fidelity tools validation.These databases have been used in order to assess the capabilities of the elsA code (ONERA-Airbus-Safran property) using its aeroelastic module and a gust model based on the Field Velocity Method. A validation process has been defined in order to move from experimental results obtained in the wind tunnel with wall boundaries to industrial modeling computed with farfield boundaries. The full process was applied to a transonic case with sine gust excitation signals.

This article presents the aerodynamic design of the airfoil of the gust generator system being developed in the GUDGET project and conceived to generate high-amplitude gusts in a transonic wind tunnel. The system is made of vanes creating a flow deviation in turn by flapping around a rotational axis or by blowing air though a suitable sonic jet located close to the vane trailing edge. The airfoil shape optimization has been carried out using a design of experiment technique (DOE) and response surface optimization along with URANS CFD. The computational model has been preliminarily validated using data provided by ONERA for the baseline design at a lower Mach number ($$\hbox {M}=0.73$$ M = 0.73 ) and then compared with the one actually required by GUDGET in the test chamber ($$\hbox {M}=0.82$$ M = 0.82 ). All the cases have been optimized at a frequency of 40 Hz and then investigated at a frequency of 80Hz.

Aeroelasticity and Structural DynamicsOn the Validation and Use of High-Fidelity Numerical Simulations for Gust Response Analysis S pecific gust response is considered as one of the most important loads encountered by an aircraft. The Certification Specification (CS) 25, defined by the European Aviation Safety Agency (EASA), and the Federal Aviation Regulations (FAR) 25, defined by the Federal Aviation Administration (FAA), describe the critical gusts that an aircraft must withstand. They must be analyzed for a large range of flight points (Altitude and Equivalent Air speed) and mass configurations. For some load cases, the standard tools could not be accurate enough to correctly predict the gust response and the use of high-fidelity computation could be required. Therefore, ONERA has implemented in its in-house Computational Fluid Dynamics (CFD) code elsA (ONERA-Airbus-Safran property) the capability to compute the high-fidelity aeroelastic gust response, directly in the time-domain, for different discrete gust shapes. This paper presents some recent work achieved at ONERA concerning high-fidelity simulations for gust response. First, a physical validation of the gust response simulation is performed by comparing the results to those obtained experimentally on a scaled model. Second, numerical comparisons are performed using various techniques, in order to model the gust. Finally, an application for generic regional aircraft is shown.