European Aeronautics 2020 Vision calls for:

• 50% cut in CO2 emission per passenger kilometer
• 80% cut in nitrogen oxide emission
• 50% drag reduction
• 50% reduction in perceived aircraft noise
• 50% reduction in product development time

A lot of aircraft simulation is needed to reach this goal. Two types of simulation are used to simulate flows in and around the aircraft: Experimental Simulation in a wind tunnel and Numerical Simulation using high performance computing. Both approaches have advantages and disadvantages and are considered complementary. But Kroll and Becker expect that both will undergo specific further developments.

To give an idea of the complexities involved in a numerical flow simulation: 7 integral equations need to be solved. About 50 million grid points are used which results in 50 - 350 non-linear equations and flow variables.

There are many places in an airplane were flow needs to be calculated and optimized. Apart from the outside airflow, this also includes fuel system design, cabine ventilation and inlet design. More and more aspects of flow in and around an airplane are being modelled.

Shape optimization is considered a key technology for future product design. Current state-of-the-art is a pure aerodynamic optimization with moderate geometrical complexity and a limited number of design variables. But according to Kroll and Becker a purer aerodynamic optimization does not necessarily improve the mission of the aircraft. What is needed is multi-disciplinary optimization: a coupling between aerodynamics structures, propulsion, fight mechanics, and aero-acoustics. But this results in a significant higher wall clock time.

Airplanes have to comply to "Airworthiness Requirements". But the design should result in a a safe aircraft structure that is as lightweight as possible, because of the costs involved. The "Airworthiness Requirements" specify in detail many of the aircraft's behaviour in flight, including the design speed envelope, the design weight envelope, the manouvering fligt envelope and the airbrake effects. This requires a lot of calcuation.

The future CFD strategy should include aerodynamic activities to build upon full simulation capability. The Airbus Credo is: "More CFD Simulations, Less Wind Tunnel Testing".

Kroll and Becker believe the way forward is the development of a "Numerical Flow Simulator" with capability as a new means for performance and assessment and to supplement Wind Tunnel testing.

A highly productive CFD Kernel should be developed with innovative, more accurate, self-adaptive numerical and physical models. Furtermore what is needed is the development of top efficiency parallel solutions including algorithms/modules suitable for complete simulations involving multiple interacting disciplines including aerodynamics, acoustics, structures, thermics, and systems.

A German national project (MUNA) is working on management and minimization of CFD uncertainties.

Somewhere between 2020 and 2030, if current HPC developments continue, full aircraft simulations are possible with systems with Exaflop/s performance.

Several new European initiatives driven by Airbus are underway to build up complementary centres for simulation development. These are:

• France, MOSART, Aerospace Valley Toulouse
• UK, CFMS, Bristol
• Spain, DOVRES, Madrid
• Germany, C2A2S2E, Braunschweig

A network of expert centres with all nations and partners involved will be built that perform targeted research serving Airbus needs. At these centres, a significant extension of hardware capacity and simulation software is expected. Direct integration of research and industry in use of software and hardware is foreseen.

The German "Center for Computer Applications in AeroSpace Science and Engineering" (C2A2S2E) is a five year project with DLR, Airbus, and the Government of Niedersachsen as partners. A total of 30 million euro will be invested.

C2A2S2E is a target-oriented research environment consisting of a collaborative research effort of research organisations, universities and industry on a common campus doing applied research in the fields of physical modelling, numerical algorithms and scientific computing.