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

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

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Approach noise of a Airbus A340-300 aircraft Slat noise is one of the dominating sources of aircraft noise during landing Introduction

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Hybrid noise prediction methods Introduction

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

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3D slat broadband noise simulation A view of the grid around the high lift wing Slat in landing conditions Flap in retracted position Freestream Mach = 0.2 Angle of attack = 12 deg. Re = 3.6×10 6 Total grid cells 5.5 million Δz/c=0.002, 26 points at span- wise Implicit solver, 2 nd order temporal accuracy and 6 th order spatial accuracy CFL=15, 5 subiterations Smagorinsky LES subgrid model Computation setup for LES

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

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

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Location of the mixing layer profile monitoring lines Mean velocity profile on the monitoring lines

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

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

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

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

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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

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

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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

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