NUMERICAL VALIDATION OF GUST RESPONSE AND NUMERICAL ASSESSMENT OF GUST LOAD ALLEVIATION FOR 2D AEROELASTIC AIRFOIL IN TRANSONIC CONDITIONS

摘要

ONERA has designed an experimental set-up dedicated to the gust load analysis and the demonstration of active gust load alleviation in transonic flows. Two main campaigns have been performed leading to the generation of database for high fidelity tools validation. The first one was dedicated to the open-loop analysis in order to measure the airfoil response due to a sine gust for both rigid and flexible cases. The second one was dedicated to the assessment of control laws implemented for gust load alleviation. These databases have been used in order to validate and to assess the capabilities of the in-house code elsA (ONERA-Airbus-Safran property) using its aeroelastic module and a gust model based on the "Field Velocity Method". In order to perform a physical validation as close as possible to an industrial modeling, the gust method implemented in elsA ("Field velocity Method") has to be validated with farfield boundary conditions. A validation process is defined in order to move from experimental results performed in the wind tunnel with wall boundaries to numerical results computed with farfield boundaries. The full process is applied to a transonic case (Mach 0.73) with an angle of attack of 2°. Sine gust signals with a frequency corresponding to the heave structural mode (25Hz) are chosen. Results are compared in terms of aerodynamics data (pressure distribution around the airfoil) and structural data (accelerometers located close to the leading and trailing edges). In order to assess the capability of the code to perform gust load alleviation analyses, a control law synthesized during the experimental campaign is implemented in the code. At each time step, the acceleration computed from the structural solver is sent to the control law which computes a flap deflection. The deflection is applied to the mesh and the aeroelastic problem is solved. In order to evaluate the code capabilities, two computations are performed: one with and one without the active closed-loop control law. A comparison of the acceleration data is carried out, in order to validate the capability of the code to alleviate the gust with a control law.