numerical investigation of broadband slat noise attenuation with acoustic liner treatment

Numerical Investigation of Broadband Slat Noise Attenuation with Acoustic liner

Treatment

University of SouthamptonSouthampton, UK

Authors: Zhaokai Ma, Xin Zhang and Malcolm Smith

Technical Supervisor: Stephen Chow

Airbus, Bristol, UK

Outline

Introduction Numerical models Computational results

– Aerodynamic flow field– Noise radiation

Summary and future work

Approach noise of a Airbus A340-300 aircraft

Slat noise is one of the dominating sources of aircraft noise during landing

Introduction

Hybrid noise prediction methods

Introduction

Numerical models

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

Computational aeroacoustic solver: SotonCAA

Linearized acoustic solver: SotonLEE

Radiation Model: FW-H

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 = 3.6×106

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

Computation setup for LES

Q iso surface colored with z-vorticity

3D slat broadband noise simulation

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

3D slat broadband noise simulation

Location of the mixing layer profile monitoring lines

Mean velocity profile on the monitoring lines

3D slat broadband noise simulation

Velocity fluctuations along the monitoring line A

3D TKE and velocity fluctuations along the monitoring line C

3D slat broadband noise simulation

Spanwise correlation of velocity fluctuations along monitoring line 1.

Spanwise correlation of velocity fluctuations along monitoring line 2.

3D slat broadband noise simulation

Power spectral density at different monitor points

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, 4nd order

temporal accuracy and 6th

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

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

Comparison of the farfield directivity

3D slat broadband noise simulation

Attenuation along the frequency

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 LESDifferent definitions of acoustic sourcesOptimization of the acoustic liner for broadband noise