A Magnus-expansion-based model for the sound generated by non-plane entropy perturbations passing through nozzles

Yeddula，Saikumar R.1; Guzmán-Iñigo，Juan1; Morgans，Aimee S.1; Yang，Dong2

10.2514/6.2022-2977

2022

28th AIAA/CEAS Aeroacoustics Conference, 2022

This paper presents an analytical model based on the Magnus-expansion method to predict the sound generated by the acceleration/deceleration of non-planar entropy perturbations in nozzles. Previous models assume that entropy perturbations reaching the inlet of the nozzle are one-dimensional, plane waves and remain plane inside the nozzle. However, studies of the convection of entropy waves throughout the combustor have confirmed that effects, such as shear dispersion and turbulent mixing, deform and attenuate the entropy perturbations as they propagate. It is thus very unlikely that entropy waves have a uniform distribution at the inlet and/or inside the nozzles but, instead, a more complex shape is expected. This alters the acoustic response significantly, particularly at higher frequencies. In this work, we adapt an existing model for entropy noise to account for non-plane effects at both the inlet and/or within the nozzle. To this end, we use the Magnus-expansion-based analytical model to solve the linearised form of the Euler equations of an inviscid, perfect, compressible gas flowing inside an isentropic nozzle. The three-dimensional entropy wave profile is sampled from numerical simulations across various frequencies. This profile is then fed to the model to capture the acoustic response. The model predictions of the nozzle’s acoustic transmission and reflection coefficients are successfully validated against numerical simulations across a wide range of frequencies.

Others

English

EI

20223112463006

Acoustic wave propagation ; Analytical models ; Aviation ; Compressibility of gases ; Nozzles ; Numerical models ; Shear flow

Air Transportation, General:431.1 ; Fluid Flow, General:631.1 ; Thermodynamics:641.1 ; Acoustic Waves:751.1 ; Mathematics:921 ; Physical Properties of Gases, Liquids and Solids:931.2

2-s2.0-85135046033

Scopus

1.Dept. Mechanical Engineering,Imperial College London,United Kingdom
2.Southern University of Science and Technology,Guangdong,China

Yeddula，Saikumar R.,Guzmán-Iñigo，Juan,Morgans，Aimee S.,et al. A Magnus-expansion-based model for the sound generated by non-plane entropy perturbations passing through nozzles[C],2022.