Global and Koopman modes analysis of sound generation in mixing layers
TypeArticles dans des revues avec comité de lecture
It is now well established that linear and nonlinear instability waves play a significant role in the noise generation process for a wide variety of shear flows such as jets or mixing layers. In that context, the problem of acoustic radiation generated by spatially growing instability waves of two-dimensional subsonic and supersonic mixing layers are revisited in a global point of view, i.e., without any assumption about the base flow, in both a linear and a nonlinear framework by using global and Koopman mode decompositions. In that respect, a timestepping technique based on disturbance equations is employed to extract the most dynamically relevant coherent structures for both linear and nonlinear regimes. The present analysis proposes thus a general strategy for analysing the near-field coherent structures which are responsible for the acoustic noise in these configurations. In particular, we illustrate the failure of linear global modes to describe the noise generation mechanism associated with the vortex pairing for the subsonic regime whereas they appropriately explain the Mach wave radiation of instability waves in the supersonic regime. By contrast, the Dynamic Mode Decomposition (DMD) analysis captures both the near-field dynamics and the far-field acoustics with a few number of modes for both configurations. In addition, the combination of DMD and linear global modes analyses provides new insight about the influence on the radiated noise of nonlinear interactions and saturation of instability waves as well as their interaction with the mean flow.
Files in this item
Showing items related by title, author, creator and subject.
ALIZARD, Frédéric; ROBINET, Jean-Christophe; GLOERFELT, Xavier (Elsevier, 2012)This work is dedicated to the presentation of a matrix-free method for global linear stability analysis in geometries composed of multi-connected rectangular subdomains. An Arnoldi technique using snapshots in subdomains ...
Comparison of Subgrid-scale Viscosity Models and Selective Filtering Strategy for Large-eddy Simulations AUBARD, Guillaume; STEFANIN VOLPIANI, Pedro; GLOERFELT, Xavier; ROBINET, Jean-Christophe (Springer, 2013)Explicitly filtered large-eddy simulations (LES), combining high-accuracy schemes with the use of a selective filtering without adding an explicit subgrid-scales (SGS) model, are carried out for the Taylor-Green-vortex and ...
The onset of three-dimensional centrifugal global modes and their nonlinear development in a recirculating flow over a flat surface CHERUBINI, Stefania; ROBINET, Jean-Christophe; DE PALMA, Pietro; ALIZARD, Frédéric (American Institute of Physics, 2010)The three-dimensional stability dynamics of a separation bubble over a flat plate has been studied in both linear and nonlinear conditions. Using a global eigenvalue analysis, two centrifugal global modes are identified: ...
ALIZARD, Frédéric; CHERUBINI, Stefania; ROBINET, Jean-Christophe (AIP, 2009)The optimal asymptotic response to time harmonic forcing of a convectively unstable two-dimensional separated boundary layer on a flat plate is numerically revisited from a global point of view. By expanding the flow ...
Three-dimensional instability of a ow past a sphere: Mach evolution of the regular and Hopf bifurcations SANSICA, Andrea; ROBINET, Jean-Christophe; ALIZARD, Frédéric; GONCALVES, Eric (Cambridge University Press, 2018-11-25)A fully three-dimensional linear stability analysis is carried out to investigate the unstable bifurcations of a compressible viscous fluid past a sphere. A time-stepper technique is used to compute both equilibrium ...