The applied aerodynamics studies of helicopters are carried out in close cooperation within ONERA. The H2T team relies on the skills of other departments, in particular the Computational Fluid Dynamics and Aeroacoustics Department (DSNA) for the development of aerodynamic computing methods and acoustic studies and the Structural Dynamics and Coupled Systems Department (DDSS) for the studies of structures and vibrations.
At international level, H2T has actively participated in many European programs (Dacro, SCIA, Helishape, Helifuse, Heliflow) and is a partner in the Friendcopter and Goahead projects. ONERA's research on helicopters is carried out jointly with the German DLR and in close collaboration with Eurocopter. The main joint aerodynamic study was the Chance program, which terminated at the end of 2004. The new project that follows on from it, Shanel, aims at better calculating the wakes that are one of the most specific aspects of helicopters. An important effort is also being put into the study of dynamic stall, within the framework of an Onera federating research project with the DDSS, DMAE and DSNA departments, carried out in cooperation with the DLR, but also partly with the US Army and Georgia Tech within the framework of a Memorandum of Agreement. H2T also participates in joint studies on quiet rotors and rotors with active blades. Other current applications concern the aerodynamic aspects of multidisciplinary research topics such as icing and the VRS as well as the overall optimization of rotors. Finally, studies are being carried out with the DSNA to simulate the helicopter parts with complex geometries with a view to minimizing noise and optimizing performances (blade roots, tail rotor).
Many computing methods are used to define the geometries of blades because of the complexities of the phenomena that have to be taken into account when optimizing the rotor aerodynamic performances whilst at the same time reducing the vibrations and noise. The first stages of optimization are carried out using simple lifting line methods with the distortion of the blades taken into account, completed by CFD Euler or Navier-Stokes calculations with the elsA software to refine the solution and calculations simulating the interactions with the complex geometry wake for studying the acoustic phenomena. Work is being done in collaboration with the Mechanical and Energy Engineering Laboratory of the Université d’Orléans to extend the capacity of the singularity methods to these complex configurations.
The current state of the art for the detailed study of the flow around a complete helicopter or its components (fuselage, rotor, tail rotor) is the unsteady Navier-Stokes calculation, which gives a sufficiently true representation of the main characteristics of the viscous flow that develops around the machine. This requires advanced numerical techniques (ALE, Chimera), and powerful computing resources. Techniques for coupling the calculation of the rotor's aerodynamics and its dynamics are also necessary for correctly representing the complexity of the phenomena: weak coupling, strong coupling.
Fenestron:
turbulent unsteady Navier-Stokes calculation
of Dauphin in climb flight
Fenestron:
turbulent unsteady Navier-Stokes calculation
of Dauphin in climb flight - pressure ratio [video]
Blade-vortex interaction:
visualization of the pressure coefficient on the blades and of the vorticity in the wake of the
retreating blade
In Modane, influence of the test bench on the 7A rotor:
Euler calculation around the 7A rotor in flight of advance with automatic grid refinement [video]
In Modane, influence of the test bench on the 7A rotor:
blade distortion with ALE technique and coupling with aeromechanics code HOST [video]
In Modane, influence of the test bench on the 7A rotor:
comparison with experimental measurements of blade-lift coefficient during a rotation
