The AERO software is the final outcome of a long engnco-American collaboration. It is dedicated to the study of resonance phenomena between a gas flow and a structure. The Aérostructure program included seven participants from industry. It opens the way to the study of coupling with turbulence.
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Thrust reverser on a commercial aircraft. We see the deformation of
the main flap deviating the reactor flow under the effect of that flow. |
In ten years, the collaboration between INRIA and the Center for Aerospace Structure of the University of Colorado at Boulder, has brought about significant progress in the study of fluid-structure interaction. Such vibratory phenomena result from the interaction of a machine with a moving gas or liquid and can damage or even destroy the structure. Whether for planes, rockets, thermal power plants or suspended bridges, the engineers’ fight against resonance is intensifying as structures are becoming larger and more elastic. There is however a major problem: the simplified fluid models available up to now to protect oneself against accidents still have a margin of error of over 10%.
INRIA’s teams in fluid mechanics and the American team in structural mechanics are thus now concentrating on sophisticated fluid models and their interaction with various kinds of structures (elastic bodies, shells, beams, etc.). Numerous mathematical advances were made during this collaboration concerning "moving domains" or "staggered time-stepping schemes" for example. These advances made it possible to use new Navier-Stokes type complex models due to dramatic gains in precision, reliability and computational cost.
The methodological characteristics of the prototype fluid-structure coupling software AERO that resulted from this long drawn-out work, have caught the interest of numerous industry representatives. In addition to Dassault-Aviation, that has been supporting these teams from the beginning, Aérospatiale, CNES, EDF, Hispano-Suiza, the SEP and the SNPE joined INRIA three years ago within the Aérostructure consortium. Due in particular to the use of benchmarks, these companies were able to realize how such software could benefit them. "AERO should make it possible to reduce long and costly experiments to test the deformations undergone by the nozzles of the Ariane rocket engines for example, by complementing a small number of very expensive tests with a series of computations," says Alain Dervieux, the head of Aérostructure. Industrial interest for this technology also shows through the setting-up of the UNSI European project on coupling in aeronautics and of the Flownet European network on aeronautic flows, with or without coupling. INRIA is participating in both.
Aérostructure stopped in September but Alain Dervieux is already planning to work on fluid pulsation phenomena due to turbulent instabilities with eddy detachment and release. In effect, Navier-Stokes type complex models are able to account for eddy transport, an increasingly important phenomenon in aerodynamics, and predict the stress undergone by the vertical fin of certain airplanes or by the thrust reverser flaps that are so useful for jumbo aircraft landing.
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