Stage M2 – Linear stability analysis of cavity flows at very high Reynolds number

Background
The coupling between hydrodynamic instabilities and acoustic waves in cavity flows leads to a resonance mechanism
that takes place on a broad range of flow conditions. Such resonance may lead to undesirable structural vibration and/or
strong tonal noise. Understanding the dynamics of this aeroacoustic phenomenon is of great interest for the aeronautic
industry, since cavities are a common feature of many aircraft geometries. In deep cavities (for which the depth-to-
width ratio is high), the resonant mechanism is underpinned by a coupling between a standing wave inside the cavity
and a hydrodynamic instability in the shear-layer above the cavity.

Program of internship
The research program will follow the different steps described below.
1- Familiarization with the mean-flow database.
2- Familiarization with the linear stability solver, developed in for a round jet. Adaptation of the linear operator and boundary conditions for the cavity configuration.
3- Analysis of the effect of Mach number and spanwise wavenumber on stability characteristics: growth rates, convection speeds and spatial organisation.
4- Comparison of stability modes with coherent structures educed from the LES through modal decompositions, such as Spectral Proper Orthogonal Decomposition (SPOD) using codes currently available at the lab