ENGINEERING AND CFD

The helicopter and aeroacoustics group at IAG simulates the complex aerodynamics and aeromechanics of rotorcraft since the early 90s. Starting from inviscid flow simulations on isolated rotors, technology improved steadily over the years, including structural dynamics coupling, turbulence modelling, trim and acoustics up to the full helicopter configurations possible today, including tail rotor and fuselage as well as consideration of the engine flow.

The grand challenge here is the combination of highly sophisticated numerical algorithms for different physical phenomena (various flow features, bi-directional coupling to structure dynamics, acoustics) applied to engineering relevant, very complex, realistic geometry configurations. Depending on the flight state, some ten revolutions of the rotor are required until the solution is fully converged to free flight conditions. This is a consequence of the fluid-structure coupling at the rotor blades – and the fuselage, recently – and the corresponding changes in attitude and steering controls to establish stationary flight without residual forces and moments.

The steady increase in computing power available allows simulation setups beyond 100 million cells with fifth order accuracy to be run routinely nowadays, and at half a billion cells in special cases. The latter one can consume up to 10 million core-hours of computing resources on the HLRS HazelHen for a single flight state. Of course, not all problems do require such enormous effort to be solved, many questions can be answered quite satisfactorily with much less complex setups and even low fidelity models. However, especially for acoustic evaluations – including shading, reflection and refraction effects on the fuselage – excellent accuracy is of paramount importance in order to reach results within the variance of individual flight test data. Such results of the working group generated within HELISIM are truly unique and mark the forefront of international research in the entire helicopter aeromechanics community worldwide.

The simulation technology developed and advanced in the helicopter group of IAG helps to understand not only basic parameters as power requirements or loads on the rotor blades, but also the very hard to estimate interactions between the different components, which are much more closely interconnected in rotorcraft than on conventional airplanes. Furthermore, flow data is delivered in much more detail than in wind tunnel experiments and flight tests, providing deeper physical insight. At the end, this knowledge enables the development of helicopters with less noise, better efficiency and more performance.

Scientific Contact:
Manuel Keßler
Institut für Aerodynamik und Gasdynamik, Universität Stuttgart
Pfaffenwaldring 21, D-70550 Stuttgart/Germany
e-mail: kessler [@] iag.uni-stuttgart.de

Website: Helicopter and Aero Acoustics Group, IAG, University of Stuttgart

Local project ID: HELISIM

February 2016