Centre Acoustique 
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Investigation of flow features around shallow round cavities subject to subsonic grazing flow Marsden et al., 2012, Phys. Fluids, vol. 24 

Mean flow rotation phi in degrees around the vertical axis as a function of kappa = height/depth. Dashed vertical lines denote separations between different regimes, and symbols, to reported computations. 

Switching regime kappa=0.32. Instantaneous velocity normalized by the free stream flow velocity, in the z/H =  0.1 plane, at times (a) t x Uinfty/D = 300 and (b) at t x Uinfty/D = 900. 
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Flight effects on screech in underexpanded jets
Schlieren picture of an underexpanded jet plume (convergent nozzle, Mj=1.50, Mflight=0.39, exposure time 6.7 µs).The first shock is seen to be twisted within the jet plume, denoting a strong oscillation amplitude, and a large flapping motion of the jet occurs further downstream.Ph.D. Thesis of Benoît André, in collaboration with Snecma and AirbusFrance. 
André et al., 2011, Phys. Fluids 
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Large eddy simulation of an overexpanded supersonic jet
Snapshot of density gradient norm in gray scale, azimuthal vorticity in color scale in the jet, and fluctuating pressure in color scale outside the jet. Pressure levels from 8000 to 8000 Pa (color bar from 5000 to 5000 Pa).Reynolds number of 10^5, exit Mach number of 3.30, static pressure and temperature of 0.5x10^5~Pa and of 360~K.Ph.D. Thesis of Nicolas de Cacqueray, in collaboration with the CNES 
Click on the picture to enlarge ! 
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Schlieren photography of a round supersonic jet at Mach number 1.5
Convergent nozzle  Md=1  Mj=1.55  NPR=4. Lower part, mean flow field obtained by averaging 1000 picturesBenoît André & Thomas Castelain 
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Superposition of density gradient (gray scale), and of pressure (color scale).
Shock Mach number of 1.2 and maximum vortex Mach number of 0.25.
Bogey, de Cacqueray & Bailly (2009, JCP)

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Strong interactions between shock oscillations, internal aerodynamic noise and acoustic duct modes are often observed in confined flows but are undesirable to prevent vibrations and fatigue of structures. In order to compute this kind of phenomena, a numerical solver called SAFARI (Simulation of Aeroacoustics in Fluids And Resonances and Interactions, EDF) has been developed. Compressible NavierStokes equations are solved using highorder finite difference schemes. A nonlinear adaptive filter is implemented to capture strong shock waves and a highorder overset grid ability is introduced in order to treat complex geometries. These numerical techniques allow to carry out direct simulation of aeroacoustic couplings in subsonic and transonic flows. A transonic flow passing a sudden expansion in a duct is studied. For certain values of the pressure ratios tau (tau = Poutlet/Pinlet), the supersonic expansion ends up after a normal shock. Strong coupling between the selfsustained oscillations of the normal shock and the longitudinal acoustic modes is captured as in the experiments. An instantaneous snapshot of the density gradient modulus is represented in a plane perpendicular to the spanwise direction. Others flow regimes have been studied. For lower pressure ratios, the flow is entirely supersonic with oblique shocks. For higher pressure ratios, the flow is asymmetric and exhibits shock cells. Emmert et al., Phys. Fluids, 2009 
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Snapshot of the density modulus, of the spanwise vorticity and of the nearfield pressure, in a plane perpendicular to the spanwise direction. The nozzle lips are represented in black. (fully expanded jet Mach number 1.55, Reynolds number 60,000) Compression shocks corresponding to highdensity gradients are observed inside the jet plume. Upstreampropagating wavefronts associated with screech tones radiation are also clearly visible on either side of the jet. A further study of the simulation data have permitted to provide evidences of the connection between the shockleakage process (Suzuki & Lele, JFM, 2003) and the generation of screech tones. Berland et al., Phys. Fluids, 2007 
The jet operates at offdesign conditions with a Mach number M = 1.55. The Reynolds number is Re = 100000. A snapshot of instantaneous spanwise vorticity is shown in purple and green, and corresponding isosurfaces of pressure are in yellow. Upstreampropagating wavefronts, corresponding to screech tones, are visible on both sides of the jet. DFG  CNRS project 
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Influence of the Reynolds number on the turbulent development of transitional,
isothermal subsonic round jets and on their radiated noise. The Mach number of the jets is 0.9,
and their Reynolds numbers are: (a) 1,700; (b) 2,500; (c) 5,000 and (d) 400,000.
The flow and the acoustic fields are calculated directly using compressible Large Eddy Simulations.
The vorticity norm is represented in the jet flow, and the fluctuating pressure is visualized outside.
Bogey & Bailly, 2006, Theoret. Comput. Fluid Dyn. 
Calcul direct du bruit d'un jet rond par simulation compressible des grandes échelles (LES)Nombre de Mach M = 0.9Nombre de Reynolds Re_{D} = 4 x 10^{5} Bogey et al., 2002, Computer & Fluids 
Calcul direct du bruit d'un jet subsonique circulaire par simulation compressible
des grandes échelles. Représentation d'une composante de la vorticité dans l'écoulement,
et du champ acoustique à l'extérieur.
Nombre de Mach M = 0.9Nombre de Reynolds Re_{D} = 6.5 x 10^{4} Bogey et al., 2003, Theoret. Comput. Fluid Dyn. 
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Calcul direct du bruit d'une couche de mélange par simulation compressible des
grandes échelles. Représentation d'une composante de la vorticité dans l'écoulement,
et du champ acoustique à l'extérieur.
Mc = 0.18 Re = 12800Bogey et al., 2000, AIAA Journal 
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Calcul direct du rayonnement acoustique d'ondes d'instabilité dans un jet plan.
M = 2Proceedings of the 3rd CAA workshop, 2000. 
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Calcul direct du bruit d'un écoulement affleurant une cavité.
Représentation du gradient transversal de la masse volumique obtenu
par DNS à gauche, et expérience de Karamcheti (NACA 3847, 1955) à droite.
M = 0.7Gloerfelt et al., 2003, J. Sound Vib. 
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