Validation of Noise Footprint Calculation Model for a High Performance Military Aircraft

Transcription

1 Validation of Noise Footrint Calculation Model for a High Performance Military Aircraft Dr. Ernst Grigat, Airbus Defence and Sace GmbH 30 th May 2017

2 Contents The following questions (hoefully) will be answered during the next minutes Why do we (have to) ut focus on military aircraft noise? Where did we start from? What is our overall aroach? Where do we stand today? What are our main results (u to now)? How do we lan to roceed? 2

3 Motivation Demand for Noise Reduction of Military Aircraft Civil Aircraft Regulations ICAO Annex 16 Subsonic airlanes with 4 engines or more Maximum Noise level of 106 EPNdB for aerolanes with maximum certificated take-off mass of kg and over. global (ICAO Annex 16) euroean (1592/2002) national (LuftVZO) Customer indication of increasing relevance Publications "Aircraft Noise" Military Aircraft ICAO Annex 16 Suersonic airlanes SARPs for these aerolanes have not been develoed. However, the maximum noise levels of ( ) subsonic jet aerolanes may be used as a guideline. Noise reduction of military aircraft is of increasing imortance RDAF RBI 2013 Swiss RfP 2008 "Aircraft Noise" "Military Aircraft Noise"

4 General Aroach Generally minor influence on noise emission (engine/airframe) for military aircraft Focus on immission Overall Goal Reduction of aircraft noise ground immission by otimization of the according takeoff climb (and landing aroach) flight aths. IS Trajectory Otimization IS NOT Calculation of absolute noise values Due to criticality/classification of military goods only few information is available on noise reduction of military aircraft Starting from scratch first ste: establish noise calculation model 4

5 Outline of Noise Calculation Model Emission Generic Modular Aroach Transmission Reflection L P = L W + D + A (Metrics) S Immission 5

6 Emission Source Modelling Overview Main Comonents Modelled Noise Sources Engine Jet (Dry & Reheat) Engine Fan Undercarriage Vertical Tail Forelane Leading Edge Trailing Edge Airframe (incl. Wing) Stores Source: Filione, Antonio: Advanced Aircraft Flight Performance Assumtions and conditions/constraints Searate modeling of source and directivity Minor sources (e.g. excrescencies) are neglected Breaku of engine noise into jet and fan noise Originally based on textbook formulas To be validated by flight test 6

7 Emission Directivity Characteristics (Near Field Behaviour) Resulting modelling aroach (engine comonents) 3-dim directivity correction No analytical solution ossible/reasonable Derivation from noise measurements necessary Very exensive and time consuming rocess Cross-read (adated civil a/c data) as interim solution To be validated/refined/corrected by flight test Source: Bräunling, Willy: Flugzeugtriebwerke Examle: general engine noise emission characteristics Examle: civil aircraft NO homogenous exansion (at least for engine/fan) All other sources modelled as monooles Uniform roagation (Directivity correction = 0) Source: Bertsch, Eberhard-Lothar: Noise Prediction within Concetual Aircraft Design 7

8 Flight Test Validation Camaign at Neuburg Airfield Setu Fly-Over Beamforming erformed by 2-day camaign (Nov. 2015) 135 microhones ( Hz) 20 EF2000 Tyhoon fly-overs 2 distinct configurations Clean 2 U/W tanks 3 engine ower settings Part Dry Maximum Dry Maximum Afterburner Undercarriage U & Down Fly-over altitude < 200ft 8

9 Environmental Requirements for Beamforming Weather conditions are critical for fly-over measurements. Recommended requirements are as follows (10 m above ground res. 30m above flight ath): temerature between -10 and +35 C C no rain, (dew), fog, drizzle or snow no ground-based temerature inversions humidity between 20% and 95% % wind conditions: maximum average wind during test oints: 12 kts maximum average cross wind comonent during test oints: 7 kts maximum wind: 15 kts 6-15 kts maximum cross wind comonent: 10 kts Furthermore the following terrain conditions aly: terrain: flat, no mounds/furrows grass: 7.5m radius circles of mowed grass (< 8cm height) around microhones loughed fields: within a 7.5m radius surface shall be reasonably tamed down 9

10 Flight Test Validation Camaign Fly-overs 10

11 Flight Test Validation Camaign - Beamforming Data rocessing/analysis and Beamforming erformed by Immission Data Sound Pressure SPL Sound Pressure Levels (measurements) FPR Pod Validation of Overall System Emission Data Sound Power Flight Path definition of source areas Meteo Data Pass # Wind Direction [Deg] Wind Seed [kts] Tem. [ C] Humidity [%] , , , , ,7 70 Validation of Noise Sources 11

12 Flight Test Validation Camaign Results Immission Exemlary grah for one of a total of 9 branches Original sound ressure samling rate 16384Hz Picture below shows 4Hz resolution (averaging) 12

13 Flight Test Validation Camaign Influence of Thrust Level on Noise Distinction of non-engine noise sources in most cases only feasible for test trials with PartDry ower setting (masking!) 13

14 Flight Test Validation Camaign Results Emission Sound Intensity Mas Overlay with Sound Power Areas Deconvolution 14

15 Noise Model Validation General Aroach Engine Comonents Non-Engine Comonents Source and Directivity modelled Y Preliminary Model Matching N Adation of Model Parameters V a l i d a t i o n Overall system Flight trials at Neuburg Flight trials by WTD91 Flight trials armasuisse V a l i d a t i o n Modelling as monoole Uniform roagation (D=0) Only sources modelled Preliminary Model Matching N Adation of Model Parameters Y Validated Model Y Matching N Adation of Model Def. of Directivities E v i d e n c e Flight trials by BAeS Manufacturer material Textbook aroaches E v i d e n c e Matching N Adation of Model Y Validated Model 15

16 Emission Modelling of Engine Combustion Noise Flight Test Corrections Comressor Comressor Combustion Chamber Byass Source: htt://eurofighter.airower.at Afterburner Low Pressure Turbine High Pressure Turbine Exit Nozzle Analysis of flight test data (see figure below) showed Combustion noise hardly measurably searately Combustion contribution to jet noise negligible Combustion covered by overall jet noise model Unified re-modelling of jet noise necessary see jet noise modelling slides Combustion Sound Power P Comb 10 C e a 2 T m Comb, out T T Comb, in Comb, in 2 Comb, in 0 2 T T with exonent C e : engine secific constant, a: seed of sound, m : mass flow, T comb,in/out : combustion chamber in/outlet temerature, Comb,in : combustion chamber inlet ressure, T turb : temerature increase in turbine Combustion Sound Power Level L W, Comb 10log P P Comb 0 Turb

17 Emission Details of Re-Modelling of Engine Jet Noise Modelling of engine jet noise as turbulent mixing noise Noise from fine scale turbulence Noise from large scale turbulence Similarity sectra for the two comonents of turbulent mixing noise Large scale turbulence (F) Fine scale turbulence (G) 17

18 Emission Directivity for Engine Jet Noise (FlightIdle - MaxDry) Directivity characteristics for Combustion included Current aroach based on reference model Measurement of free stream characteristics Adated to actual case (military aircraft engine) Taken from textbook only rough aroximation Flight Test Corrections Offset model-ft between ~ emission angle Re-modelling (additional deendency on thrust lever) Emission Angle [ ] Directivity Corr. [db] Realistically to be determined emirically by resective flight tests 18

19 Emission Modelling of Undercarriage Noise Flight Test Corrections Landing Gear Sound Pressure LG A 2q Ma F( f r ref ) withq: dynamic ressure, Ma: free stream Mach number, A: equivalent landing gear surface area, r ref : reference length : emirical reference amlitude for frequency sectrum, and the frequency (f) correction function using Strouhal number St rod system Parameter adatation:,, St 0 F f q q St q 0 St q / 1 St 0 St q with l ref : reference length, V: free stream velocity,,q: emirical arameters St St f f l V ref attachment arts Landing Gear Sound Pressure Level L, LG 20log LG 0 Assumtion: monoole model uniform roagation Directivity correction D = 0 tyre 19

20 Emission Modelling of Forelane Noise Flight Test Corrections Forelane Sound Pressure (Trailing Edge Noise) FP 2.5 A 2 2 u q Ma CL rref V withq: dynamic ressure, Ma: free stream Mach number, A: total forelane surface area, r ref : reference length C L : lift coefficient, u 0 : local velocity variation du to turbulence, Comlemented by vortex noise model Forelane Sound Pressure Level L, FP 20log FP 0 Assumtion: monoole model uniform roagation Directivity correction D = 0 20

21 Emission Modelling of Trailing Edge Noise Flight Test Corrections No isolated noise signal for trailing edge extractable Actual sound ower model seems resonable (see below) Read-across of sectral form from forelane feasible including vortex noise model comlement Trailing Edge Sound Pressure TE 2.5 A 2 2 u q Ma CL rref V withq: dynamic ressure, Ma: free stream Mach number, A: total trailing edge surface area, r ref : reference length C L : lift coefficient, u 0 : local velocity variation du to turbulence, Trailing Edge Sound Pressure Level L, TE 20log TE 0 Assumtion: monoole model uniform roagation Directivity correction D = 0 21

22 Emission Modelling of Leading Edge Noise Semiemirical aroach Based on wind tunnel tests for commercial aircraft Adated to high erformance military aircraft Normalized LE Sound Pressure Level from WTT L, norm log( St) LE TE St St s St s L, norm log( St) St St s St f cle V withc LE : average LE chord, LE : slat deflection, TE : fla deflection LE TE Flight Test Corrections Flight Test data rove unrealistic LE modelling LE noise contribution is modelled much too high Not enough FT data for realistic re-modelling LE retracted: noise masked by other sources LE extended: no measurements ( neglected) Velocity (L,V ) and geometric (L,geo ) correction V cosle L, V 50log 30 log L Vref cosle, ref with s LE : san slat, LE : leading edge swee cle sle log cosle r, geo 2 ref Leading Edge Sound Pressure Level L, LE L, norm L, V L, geo LE de facto a diole showing distinctive directivity Currently no WT / FT data for military aircraft available Simlification of directivity feasible for T/O, not for landing To be refined in a later stage of model develoment Incororation of LE noise into surface noise feasible Increment on roughness height in surface noise Assumtion: monoole model uniform roagation Directivity correction D = 0 22

23 Emission Modelling of Vertical Tail Noise Flight Test Corrections Vertical Tail Sound Pressure (Trailing Edge Noise) Currently no correctio/refinement/validation No according flight test data available Effect negligible due to minor relevance No significant contribution to overall noise Surface noise comonent / contribution neglected! Fin 2.5 A 2 2 u q Ma CL rref V withq: dynamic ressure, Ma: free stream Mach number, A: total vertical tail surface area, r ref : reference length C L : lift coefficient, u 0 : local velocity variation du to turbulence, Vertical Tail Sound Pressure Level L, Fin 20log Fin 0 Assumtion: monoole model uniform roagation Directivity correction D = 0 23

24 Emission Modelling of Airframe Noise Flight Test Corrections Airframe Sound Pressure (Surface Noise) Airframe q Ma r A C ref D.3 R rel ( f ) withq: dynamic ressure, Ma: free stream Mach number, A: airframe lower surface area, r ref : reference length C D : drag coefficient, : roughness density, R rel : relative roughness height, and the frequency (f) correction function using Strouhal number St Airframe Sound Pressure Level L St St St f with : boundary layer thickness, V: free stream velocity, Airframe 20log Airframe 0 St St f 2 f V Assumtion: monoole model uniform roagation Directivity correction D = 0 sectral shae Model adatation: correction function St St St f 5 24

25 Emission Modelling of Stores Noise Noise Characteristics for a 1000l tank Strategy for including other stores: scaling with Drag Index 1000l tank Sound Pressure (Surface Noise) Tank q Ma A C r ref D.3 R rel ( f ) withq: dynamic ressure, Ma: free stream Mach number, A: tank surface area, r ref : reference length, C D : drag coefficient, : roughness density, R rel : relative roughness height, and the frequency (f) correction function with Strouhal number St St St St f St St f 2 f V with : boundary layer thickness, V: free stream velocity Flight Test Corrections During flight trial data evaluation only trailing edge tye noise could be identified. Surface noise is comletely masked. Re-definition of noise model Read-across from forelane trailing edge validation But: additionally tonal comonents due to eriodical flow searations The general aroach for covering other stores by scaling with Drag Index cannot be directly taken Tonal Comonents 1000l tank Sound Pressure Level L, Tank 20log Tank 0 Assumtion: monoole model uniform roagation Directivity correction D = 0 25

26 Immission Modelling and Imlementation Asects Noise immission is calculated by summing u the contributions from the different/distinct noise sources imacting on ground. Calculation results for each arameter (e.g. SPL) are stored in datacubes Evaluation of immissions based on different metrics, e.g. - Sound Pressure Level (SPL) - A-weighed SPL - Effective Perceived Noise Level - Psychoacoustic metrics Reflection (mountains) is executed by Transmission algorithm (but not yet imlemented) Phenomena not considered/imlemented due to reduction of comlexity Diffusion (molecular level) Diffraction 26

27 Immission Grahical Reresentation of Noise Footrints Based on Matlab using Google Mas Ai Functions WGS (World Geodetic System) 84 Coordinates Terrain Reresentation otentially based on NASA SRTM currently checked (resolution ~30m) interface yet rovided 27

28 Transmission Modelling of Noise Proagation Time t 0 Original aroach: t immission = t emission Noise 0 0 Noise ms ms d 0 distance d 1 But obviously more realistically (a = seed of sound) Noise 0 0 +d 0 /a Noise ms ms+d 1 /a Imroved aroach: Simlified (linearised) Ray Tracing Reference Point Inconsistencies due to discretisation t ms+d 3 /a t ms+d 2 /a Modelled noise loss by absortion (ISO ) Geometric (deending on distance from source) Atmosheric (molecular absortion) Soil daming (for small immission angles) Doler Effect included Noise reflection not yet modelled, but lanned for Wind & temerature effects (refraction) neglected t ms+d 1 /a 28

29 Transmission / Proagation Algorithm Validation Noise Footrint Program - Original Version - Comarison with Program SOPRANO by Refinements / Adjustments Geometric absortion Atmosheric absortion Doler effect Noise Footrint Program - Validated Udate - Validated transmission algorithm 29

30 Transmission / Proagation Algorithm Validation - Results Examle: noise footrint of a turning flight 15 secs after takeoff Original imlementation Refined algorithm 30

31 Summary Resuming the introductory questions Why do we (have to) ut focus on military aircraft noise? Increasing ublic ressure / flight regulations / customer requirements Where did we start from? Starting from scratch What is our overall aroach? Noise reduction by flight ath otimisation Strictly modular analytical modelling aroach to be validated by flight test Where do we stand today? Simlified (flying) aircraft noise model almost comletely validated What are our main results (u to now)? First calculations look romising... and one more question 31

32 Outlook How do we lan to roceed? Final refinements of emission model including directivity characteristics Comlete validation of the noise model based on flight test noise measurements Revision / additional investigation on feasibility of monoole assumtion for landing gear Integration of wind and temerature effects into transmission algorithm Parallelization Integration of a terrain data base into the model Integration of a terrain data base into the grahical noise footrint reresentation Comfortable grahics based user interface for noise calculation model Embedding of the noise calculation model into an flight ath otimisation algorithm and many more Current work in rogress 32

33 Thank you for your attention! Any questions? 33