Source Modelling II: Airframe Noise W. Dobrzynski * and S. Guérin ** Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR) *Institut für Aerodynamik und Strömungstechnik Braunschweig/Göttingen **Institut für Antriebstechnik / Abt. Turbulenzforschung Berlin MIT / DLR / DLH Workshop on Noise Abatement Procedures 17 – 19 August 2004, Seeheim / Germany MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Analysis of Wind Tunnel and Flyover Noise Data Objectives: Development of noise source models for Airbus aircraft landing gears and high lift systems. Approach: Quantification of noise radiation characteristics through analysis of wind tunnel data on scaled and full scale aircraft/components and A319 flyover noise data (array and single lateral microphones). MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Landing Gear Noise Data from Full-scale Wind Tunnel Tests Noise data available from full-scale wind tunnel tests (DNW-LLF): Main landing gears: A320 -> 2-wheel and 4-wheel configurations A340 -> 4-wheel and 6-wheel configurations Nose landing gears: A340 -> 2-wheel configuration Wind tunnel noise data analysis: Effect of speed Radiation directivity MLG installation effects (wing circulation) Harmonisation with flyover test results Modelling of noise characteristics for impact prediction A320 MLG A340 MLG A340 NLG MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Empirical Landing Gear Noise Model Frequency [Hz] Spectra of main / nose gear MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Landing Gear Noise Directivity Test range in DNW-LLF Dipolmodel: Low Frequencies High Frequencies Flow MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Installation Effects U = U¥ – v Zirkulation G z v Local velocity at gear position under the wing as function of circulation: Zirkulation G z v U = U¥ – v (Kutta-Joukowski) and (with chord s and span l) Thus circulation can be expressed as and which results in MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Clean aircraft with LG down: Landing Gear Noise Data from Flyover Noise Measurements (Array) Microphone array source localisation and data analysis: Compute source maps for selected radiation directions Determine acoustic energy of components re total aircraft j = 90° f = 4 kHz Clean aircraft with LG down: Spectra from Array Data Analysis: 1/3-oct. Band Frequency NLG MLG-1 MLG-2 MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Comparison of Landing Gear Noise Spectra from W/T and F/T Normalized 1/3-oct. SPL Strouhal Number Airbus Nose Landing Gear Airbus Main Landing Gear j = 90° Future work: Harmonisation of results from wind tunnel and flight tests. MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

High Lift Devices Noise Data from Wind Tunnel and Flyover Noise Tests Noise data available from model and full scale wind tunnel (DNW-LLF) and A319 flyover noise tests. A320 Modell A320 A319 Noise data analysis: Effects of - aircraft speed - aircraft angle-of-attack - slat/flap deflection Quantification and extrapolation of measured directivities Development of scaling laws Validation / harmonisation with flyover test results Modelling of noise characteristics for impact prediction MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Baseline “landing” noise spectrum: Semi-empirical Slat Noise Model The analysis of aircraft noise characteristics showed: slats represent dominating noise components spectra scale with slat chord noise intensity scales with v4.5 levels peak in the rear arc Baseline “landing” noise spectrum: Maximum noise level: Compact dipole model: Aircraft Axis Slat a x e d z j Effect of slat deflection: Linear dependence of level on deflection angle Only low frequency (Strouhal number) effect MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Normalised Spectra for j = 90° Polar Directivity for St = 1.8 Slat Noise Model Validation Normalised Spectra for j = 90° Polar Directivity for St = 1.8 Comparison between wind tunnel and flyover data show good agreement in terms of level, spectral shape and directivity. MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Summary Aiming at the development of airframe noise source models for the prediction of noise contours, wind tunnel and flyover noise data are analysed. Landing gear noise: Determine radiation characteristics (speed, directivity), Quantify effects of gear geometry on noise Describe under the wing installation effects. High lift devices noise: Rank order high lift components in terms of noise Determine radiation characteristics (speed, slat/flap deflection, directivity) Determine scaling laws For both landing gears and high lift devices initial (semi)-empirical source models have been developed. MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim