Combined CFD-Stochastic Analysis of an Active Fluidic Injection System for Jet Noise Reduction

Mattia Barbarino,Raffaele Tuccillo,Mario Ilsami,Luigi Federico

doi:10.3390/app7060623

Mattia Barbarino, Raffaele Tuccillo + Show 2 more

Open Access

https://doi.org/10.3390/app7060623

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Abstract

In the framework of DANTE project (Development of Aero-Vibroacoustics Numerical and Technical Expertise), funded under the Italian Aerospace Research Program (PRORA), the prediction and reduction of noise from subsonic jets through the reconstruction of turbulent fields from Reynolds Averaged Navier Stokes (RANS) calculations are addressed. This approach, known as Stochastic Noise Generation and Radiation (SNGR), reconstructs the turbulent velocity fluctuations by RANS fields and calculates the source terms of Vortex Sound acoustic analogy. In the first part of this work, numerical and experimental jet-noise test cases have been reproduced by means RANS simulations and with different turbulence models in order to validate the approach for its subsequent use as a design tool. The noise spectra, predicted with SNGR, are in good agreement with both the experimental data and the results of Large-Eddy Simulations (LES). In the last part of this work, an active fluid injection technique, based on extractions from turbine and injections of high-pressure gas into the main stream of exhausts, has been proposed and finally assessed with the aim of reducing the jet-noise through the mixing and breaking of the turbulent eddies. Some tests have been carried out in order to set the best design parameters in terms of mass flow rate and injection velocity and to design the system functionalities. The SNGR method is, therefore, suitable to be used for the early design phase of jet-noise reduction technologies and a right combination of the fluid injection design parameters allows for a reduction of the jet-noise to 3.5 dB, as compared to the baseline case without injections.

Highlights

The problem of noise generation by compressible turbulent jets has been the subject of studies since the early 1950s, with the introduction of the turbojet in commercial aircraft
The problem of jet noise prediction has been numerically addressed through a broad range of methods
A promising technology seems to be the fluidic chevron, as alternative solution to the mechanical chevron. This device consists of small injectors that inject high pressure air or other fluids, such as water, near the nozzle exit edge in order to emulate the mixing and the noise reduction features of the mechanical chevron

Summary

Introduction

The problem of noise generation by compressible turbulent jets has been the subject of studies since the early 1950s, with the introduction of the turbojet in commercial aircraft. RANS computations are not able to model, solely, the aeroacoustic phenomena In this context, the stochastic approach for the prediction of noise from turbulence has received a great deal of interest in recent years. A promising technology seems to be the fluidic chevron, as alternative solution to the mechanical chevron This device consists of small injectors that inject high pressure air or other fluids, such as water, near the nozzle exit edge in order to emulate the mixing and the noise reduction features of the mechanical chevron. Despite the simplicity of the mechanical chevron, the fluidic injection technique allows a greater flexibility It can be used when the jet-noise reduction requirement is needed, for example during take-off and landing phases. The novelty of this paper is the proof of the potential of the SNGR approach as applied to the design of new devices suitable for jet noise reduction

Model Description

Model Validation

Active Fluidic Injection System

Findings

Conclusions