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Fluid mechanics

Computing Better Engines

The European Research Network in Computational Fluid Dynamics is exploring new avenues to make engines more efficient and less noisy. This Franco-German partnership associates 19 different research teams from both countries.

No switching errors or technical hitches to report. For the last 20 or so years, French and German researchers from CNRS and Deutsche Forschungsgemeinschaft (DFG) have been taking part in a considerably innovative research program on fluid dynamics. Their primary objective is to reduce turbulence phenomena in air and land transport. To do so, they need to acquire a very detailed understanding of the turbulence phenomena that occur behind airplane engines and cars, in order to reduce the resulting noise, particularly in civil aviation turbojet engines. The expected result is to improve aerodynamics and lower fuel consumption, not just in planes but also in cars.

computing engines

© M. Minguez, E. Serre, R. Pasquetti

Researchers working on computational fluid dynamics study turbulence phenomena in transportation vehicles. Computer models are generated simulating turbulence around a car engine.

Since the late 1980s, the two countries have been coordinating the efforts of their scientific communities around increasingly finely targeted research themes. From bilateral exchange programs to collaborative projects, they eventually created a European Research Network (GDRE) in Computational Fluid Dynamics for the current period (2004-2011). Twenty years after the first collaboration, 19 different research teams working in 14 French and German laboratories1 are currently involved in this program. Its annual budget–estimated at €2.5 million–is funded on the one hand by CNRS, the French Ministry of Research, and ONERA, and on the other by DFG.
“This initiative brings together experts in fluid mechanics, acoustics, modeling, and high-performance computing,” explains Patrick Bontoux, director of M2P22 in Marseille. One of the leading scientific approaches is Large Eddy Simulation (LES), a type of numerical meshing that makes it possible to simulate the large and most energetic turbulent scales–also known as eddies–while at the same time modeling the smallest ones, which formerly went unrecorded by the system. The GDRE's expertise in this field has largely benefited from the considerable computational power found in various national centers, such as IDRIS,3 as well as from the vector supercomputers recently acquired by CNRS, like IBM Blue Gene, the 9th most powerful supercomputer in the world which has a combined computational power of more than 15,000 last-generation laptops.
LES makes it possible to isolate and study specific phenomena like the jet flows emitted by airplane engines, which have an impact on both noise and atmospheric pollution. Another phenomenon being studied is viscous drag, the resistive force that air exerts on vehicles in movement. “We try to predict and reduce drag and the flow separation that occurs near the sides of vehicles, which also generates eddies,” explains Bontoux. A complex task, but one well worth the effort: The reduction of such effects by fine-tuning the geometry of the vehicle leads to lower fuel consumption.
Since 2004, the GDRE's teams have published six books and nearly 200 articles, and have organized more than a dozen seminars. The GDRE has already advanced our understanding of the physical mechanisms involved in turbulences, and improved the techniques and models currently used in industry. This success can be in part credited to the close ties established with various companies and organizations like Dassault Aviation, Snecma, Rolls Royce, MTU, Airbus, Renault, CEA, CNES, DGA, EDF, and ONERA.
In the long run, this program aims to “make numerical simulation a common language at a European level.” Discussions are underway to expand the GDRE beyond 2011. The new PRACE initiative (Partnership for Advanced Computing in Europe) suggests concentrating supercomputing facilities in several international centers to give European scientists the computing power necessary to meet tomorrow's challenges.

Séverine Lemaire-Duparcq

Notes :

1. Some of the participating laboratories on the French side: LEA in Poitiers, LMFA in Lyon, M2P2 in Marseille, LMF in Nantes, LEGI and LJK in Grenoble, IMFT in Toulouse, LJAD in Nice, LIMSI. On the German side: RWTH in Aachen, TU in Berlin, Darmstadt, Munich, and Dresden, as well as the universities of Stuttgart, Karlsruhe, Hamburg, and Erlangen.
2. Mécanique, modélisation et procédés propres (CNRS / Université Marseille-I and -II / Ecole Centrale Marseille).
3. Institut du développement et des ressources en informatique scientifique.

Contacts :

Patrick Bontoux,
M2P2, Marseille.


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