A Porous Media Model for the Numerical Simulation of Acoustic Attenuation by Perforated Liners in the Presence of Grazing Flows

Jianguo Wang,Qin Qin,Philip Rubini

doi:10.3390/app11104677

Abstract

In this paper, a novel model is proposed for the numerical simulation of noise-attenuating perforated liners. Effusion cooling liners offer the potential of being able to attenuate combustion instabilities in gas turbine engines. However, the acoustic attenuation of a perforated liner is a combination of a number of interacting factors, resulting in the traditional approach of designing perforated combustor liners relying heavily on combustor rig tests. On the other hand, direct computation of thousands of small-scale holes is too expensive to be employed as an engineering design tool. In recognition of this, a novel physical velocity porous media (PVPM) model was recently proposed by the authors as a computationally less demanding approach to represent the acoustic attenuation of perforated liners. The model was previously validated for the normal incidence of a sound wave by comparison with experimental data from impedance tubes. In this paper, the model is further developed for configurations where the noise signal propagates in parallel with the perforated liners, both in the presence and absence of a mean flow. The model is significantly improved and successfully validated within coexisting grazing and bias flow scenarios, with reference to a series of well-recognized experimental data.

Highlights

The acoustic properties of a series of perforated liners measured by the authors themselves and four well-acknowledged benchmark experiments are directly compared with those results acquired by the physical velocity porous media (PVPM) model using numerical methods
The PVPM model provides a robust prediction of the resonance frequencies and major features such as the sensitivity of the resonant frequency as a function of the liner porosity. These results demonstrate that the PVPM model is able to capture the attenuation effects of perforated liner absorbers where the acoustic signal in parallel comparison with the liner surface
The resonance frequencies and major features such as the sensitivity of the resonant frequency as a function of the liner porosity. These results demonstrate that the PVPM model is able to capture the attenuation effects of perforated liner absorbers where the acoustic signal propagates in parallel with the liner surface

Summary

Introduction

Helmholtz resonators are able to provide very high attenuation at their resonant frequency. Perforated combustor liners were originally conceived as a means to provide enhanced cooling of gas turbine liners [7]. With the appropriate design, they are lighter and more compact but they offer the potential to attenuate pressure fluctuations over a much broader frequency range compared to single-neck Helmholtz resonators [8,9]. Computational fluid dynamics (CFD) is based upon the numerical solution of the underlying governing equations for a fluid flow, under specified boundary conditions. The propagation of an acoustic wave in a flow tube may be represented as an unsteady three-dimensional compressible flow, and the corresponding governing equations may be expressed in three-dimensional Cartesian coordinates as [33].

Methods

Results

Conclusion