Research

My main research themes are :

  • Flow control of separated flows
  • Hydrodynamic instabilities
  • Transition to turbulence in shear flows
  • Automotive aerodynamics
  • Micro-flows
  • Acoustophoresis

Open-loop and closed-loop control of separated flows using visual sensors (with N. Gautier)

Closed-loop control of the separated flow downstream a Backward-Facing Step (BFS) using a pulsed slotted-jet as the actuator and real-time PIV measurement as input :

D=5_recirc_opt

Recirculation bubble downstream a BFS: natural uncontrolled flow (grey area) together with the controlled flow (black area).

Time serie showing the instantaneous velocity field donwstream the BFS for the uncontrolled and controlled flow:

controlled-uncontrolled_movie

 

Acoustic manipulation of particles or living cells in microchannels

Acoustophoresis of particles (with M. Hoyos and former Ph. D. student O. Dron)

Principe_Foc

Principle of the acoustic focusing of particles in suspension in a micro-cavity or a micro-channel.

Movie showing the focusing of the particles at mid-height of the channel: focusing_crop (converti)

We also demonstrated that it is possible to move the sheet of particles along the height of the channel by varying the acoustic frequency:

zfoc_plates_color

It opens the way to many new applications under investigation.

 

Hydrodynamic instabilities

Instabilities of a Jet-In-Crossflow (JICF) in collaboration with T. Cambonie

 

Transition to turbulence in shear flows

Subcritical transition to turbulence in a Plane Poiseuille Flow (PPF), with G. Lemoult and J. E. Wesfreid

Visualization of a the structure of a turbulent spot growing in the subcritical régime :

Spot

Visualisation of the nucleation of a turbulent spot growing in the PPF after an initial pulse in the middle of the channel :

movie1 – 1

 Self-Sustained Process (SSP) in boundary layer with T. Duriez and J. E. Wesfreid.

We have shown experimentally that the SSP is indeed a key mechanism in the transition to turbulence of wall-bounded shear flows. It was achieved using small cylinders to force the transition of a subcritical boundary layer :

figure2

Creation of streaks of high and low streamwise velocity downstream the cylinders.