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Guillaume Dufour


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Main research themes :

 Body force modeling of turbomachinery flows

For many of the upcoming generations of aircraft and engines, such as UHBR with short intake, CROR or Boundary Layer Ingestion configurations, the interactions between the turbomachinery elements and the aircraft are expected to be very significant.
In this context, there is a need for fast but reliable ways of modeling turbomachinery blades in CFD calculations. The Body Force Method (BFM) is a promising way to tackle this problematic.

In the BFM approach, the turbomachinery rows are replaced by a volumic source term, which can be expressed analytically or extracted from reference simulations. Very significant cost reduction can be achieved (of about 1 to 2 orders of magnitude), because of a reduction in mesh size and the possibility to handle azimuthal distortion with a steady approach.

Several ongoing projects support this activity :
- A PhD (William Thollet) in collaboration with Airbus has started in 2014 on this method, focusing on fan/intake interactions for short intakes, as illustrated below.
- A post-doctoral position for 3 years (Foad Mehdi Zadeh), supported by the French Ministry of Defense, focusing on the simulation of a complete turbofan engine (WEBFM - Whole Engine Body Force Modeling).
- A PhD (Luis Lopez de Vega), in collaboration with Airbus, will start in early 2017. It will study aircraft-induced unsteady phenomenon, and the coupling with an engine system modeling tool.
- A master student (Adrien Chatel) will start working on BFM modeling of rotating stall in February 2017.
- Studies on inflow distortion prediction on ventilation fans are about to start

 Simulation of unsteady and separated flows in turbomachines

In the framework of the problematic of off-design flows in turbomachines as defined in the TMP group, the present research aims at developping and qualifying unsteady numerical methods, focusing on deterministic row interactions and off-design separated flows.

  • Aerodynamics of blade rows at windmill When a turbofan engine flames out during flight, the ram pressure at the fan inlet creates an internal flow that causes spool rotation and windmilling operation (corresponding to a freewheeling mode of the rotor). Simulating and understanding the aerodynamics of turbomachinery blade rows in windmilling is a key factor in the assessment of the relight capabilities of turboengines.
  • Validation against test bed turbofan tests : The DGEN 380 of Price Induction is a High-bypass-ratio geared turbofan engine. A fully-instrumented version of the DGEN 380 is on the test rig of ISAE, providing valuable data for validation.
  • Harmonic methods :
    Harmonic methods fall within the broad class of Fourier-based methods. They rely on a flow decomposition into generalized Fourier series, allowing for an efficient resolution of periodic unsteady flows, with significant computational time reductions. We study a frequency domain algorithm (the Nonlinear Harmonic Method), as well as a time-domain approach within the framework of a cooperation with the CERFACS.

 Turbulence modeling for turbomachinery flows

This research activity is peformed within the Turbulence, instabilities and numerical simulation group. In close interaction with the themes described above, the goal is develop and assess turbulence models strategies for turbomachinery flows.

  • First-order modeling of rotation and curvature effects : Following a research theme started during my PhD, we focus here on the inability of eddy-viscosity to naturally account for rotation and curvature effects. Current efforts are devoted to two-equation models.
  • Hybrid simulation : wall modeled LES : preliminary studies on the modeling of the boundary layer in RANS within an LES framework have been performed, focusing on the inclusion of rotation effects (collaboration lead by Julien Bodart).

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