Numerical Investigation of Broadband Slat Noise Attenuation with Acoustic liner Treatment

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

3. Introduction Slat noise is one of the dominating sources of aircraft noise during landing Approach noise of a Airbus A340-300 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 3D TKE and velocity fluctuations along the monitoring line C Velocity fluctuations along the monitoring line A

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

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 Attenuation along the frequency Comparison of the farfield directivity

16. Summary and future work • Summary • 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