Entropy noise modelling in 2D choked nozzle flows

Abstract

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Influence of viscosity on entropy noise generation through a nozzle

“…when entropy fluctuations interact with a shock located in the diffuser. In such cases, entropy fluctuations are modified through the shock and need to be computed jointly with acoustics, see for instance Huet et al [26].…”

“…Entropy fluctuations being purely convected by the flow, they remain confined in the same streamtube throughout the nozzle. Under these assumptions, entropy can be expressed analytically at every position inside the nozzle for each streamtube and writes in the harmonic regime [25,26]…”

“…( 6). This numerical resolution is performed in the present study with the inhouse code CHEOPS-Nozzle (non-compact harmonic entropy noise predictions) [25,26].…”

“…Additionally, Mahmoudi et al [23] describe the nozzle geometry as a succession of ducts of constant radii and apply the compact solutions of Marble and Candel between ducts to reconstruct frequency-dependant transfer functions. The one-dimensional hypothesis was recently relaxed by Duran and Morgans [24], Dowling and Mahmoudi [1] and Mahmoudi et al [23] by considering azimuthal flow fluctuations in annular nozzles and by Emmanuelli et al [25] and Huet et al [26] to account for the radial evolution of the flow. The former studies allow to investigate the contribution of the different azimuthal modes in indirect noise, whereas the latter addresses the problem of shear dispersion of entropy fluctuations by the mean flow and subsequent noise modifications.…”

Scattering of entropy waves into sound by isolated aerofoils

“…In the mid-frequencies, three-dimensional effects become apparent and must be described by the model (Emmanuelli et al. 2020; Huet, Emmanuelli & Le Garrec 2020). Further extensions of the quasi-one-dimensional theory include nonlinear effects (Huet & Giauque 2013), compositional inhomogeneities (Magri et al.…”