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CoJeN
Computation of Coaxial Jet Noise

Background

Despite the progress in the development of CFD solvers, most of the jet noise prediction methods currently in use in the aerospace industry are correlations based on empirical databases. Significant advances have recently been made towards developing aero-acoustic methods, which use CFD results as the input for prediction of the acoustic fields generated by exhaust flows. However, these studies have concentrated mainly on fundamental cases, such as single-stream jets. The industrial requirement is to predict the noise from complex geometries, such as coaxial jets with pylons, forced mixers and serrated nozzles.

Project objectives

The principle objective of CoJeN is:

  • To develop and validate prediction tools, which can be used by the aerospace industry to assess and optimise jet-noise reduction techniques.

In order to bring the methods developed in JEAN (a Framework Programme 5 project) and the national programmes to the point where they are useful to industry, the methods must be extended to cope with hot coaxial jets and arbitrary nozzle geometries. The methods must also be validated to demonstrate their accuracy and reliability.

Accordingly, the specific technical objectives of the project are:

  • To identify and improve optimal CFD techniques for the prediction of jet flow development from coaxial nozzles of arbitrary geometry
  • To develop aero-acoustic codes, which can predict the acoustic fields from the CFD results
  • To acquire aerodynamic and acoustic data with which to validate these codes.

Description of the work

In CoJeN, CFD techniques for the prediction of the turbulence characteristics of coaxial jets are being developed and validated. These will be linked to noise source generation and propagation models for the prediction of the near- and far-field noise. The results from these will be critically evaluated against data, which will be obtained from a series of carefully designed experiments. The project is divided into the following Work Packages and tasks:

Project management, specifications and assessment

Flow prediction

  • Reynolds Averaged Navier-Stokes (RANS) techniques
  • Large eddy simulation (LES) and detached eddy simulation (DES) techniques
  • Vortex methods
  • Technology transfer

Acoustic source generation and propagation modelling

  • Acoustic analogies
  • Direct methods
  • Hybrid methods
  • Technology transfer

Acquisition of validation data

  • Advanced measurement techniques
  • Single and multi-point flow measurements
  • Whole field flow measurements
  • Acoustic measurements
  • Testing and data reduction.

Expected results

  1. Validation of efficient flow solvers for coaxial jet development.
  2. Integration of these to updated classical and novel source and propagation models.
  3. Prediction methodologies for jet noise applications.
  4. Measurement of turbulent length scales in jets as a function of frequency.
  5. Further development of new methods for the identification of aero-acoustic source mechanisms using the multi-point measurements.
  6. Use of new signal processing techniques for turbulence/acoustic measurements.

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