1. University of Southampton Southampton, UK
Numerical Investigation of Broadband Slat Noise Attenuation with Acoustic liner Treatment
Authors: Zhaokai Ma, Xin Zhang and Malcolm Smith
University of Southampton
Southampton, UK
Technical Supervisor: Stephen Chow
Airbus, Bristol, UK

2. Computational results
Outline
Introduction
Numerical models
Computational results
Aerodynamic flow field
Noise radiation
Summary and future work

3. Introduction
Slat noise is one of the dominating sources of aircraft noise during landing
Approach noise of a Airbus A aircraft

4. Introduction
Hybrid noise prediction methods

5. Numerical models Computational aeroacoustic solver: SotonCAA
Governing equations: Navier-Stokes equations
Spatial discretization: 4th, 6th -order compact schemes
Time integration: Implicit 2nd -order LU method
Explicit 4th –order Runge-Kutta method
Turbulence model: Spalart-Allmaras, DES, LES
Linearized acoustic solver: SotonLEE
Radiation Model: FW-H

6. 3D slat broadband noise simulation
Computation setup for LES
Slat in landing conditions
Flap in retracted position
Freestream Mach = 0.2
Angle of attack = 12 deg.
Re = 3.6×106
Total grid cells 5.5 million
Δz/c=0.002, 26 points at span-wise
Implicit solver, 2nd order temporal accuracy and 6th order spatial accuracy
CFL=15, 5 subiterations
Smagorinsky LES subgrid model
A view of the grid around the high lift wing

7. 3D slat broadband noise simulation
Q iso surface colored with z-vorticity

8. 3D slat broadband noise simulation
Rapid distortion of coherent structures via mean-flow straining
Secondary separation
Vortex merging
Cove vortex
Edge scattering
z-vorticity contours near the slat cove region

9. 3D slat broadband noise simulation
Location of the mixing layer profile monitoring lines
Mean velocity profile on the monitoring lines

10. 3D slat broadband noise simulation
Velocity fluctuations along the monitoring line A
3D TKE and velocity fluctuations along the monitoring line C

11. 3D slat broadband noise simulation
Spanwise correlation of velocity fluctuations along monitoring line 1.
Spanwise correlation of velocity fluctuations along monitoring line 2.

12. 3D slat broadband noise simulation
Power spectral density at different monitor points

13. 3D slat broadband noise simulation
Computation setup for LES source driven APE
3D APE with LES calculated sources
Total grid cells 1.2 million
Δz/c=0.002, 26 points at span-wise
Explicit solver, 4nd order temporal accuracy and 6th order spatial accuracy
Source terms:
Ti me domain impedance boundary condition of Fung et. al.
A view of the grid for LES sources driven APE calculation

14. 3D slat broadband noise simulation
A view of the liner treatment and the grid near the slat cove
Pressure perturbation around the high lift wing

15. 3D slat broadband noise simulation
Comparison of the farfield directivity
Attenuation along the frequency

16. Summary and future work
Broadband slat noise generation was simulated using LES
Broadband slat noise attenuation ability of acoustic liners was explored
Future work
Refined grid calculation of LES
Different definitions of acoustic sources
Optimization of the acoustic liner for broadband noise