Rayleigh-Ludwig ~ 3 min

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1 August 2015 Journal of Beijing University of Aeronautics and Astronautics Vol 41 No 8 http bhxb buaa edu cn jbuaa@ buaa edu cn DOI /j bh * Rayleigh-Ludwig 45 35% ~ 55% Rayleigh-Ludwig % Rayleigh-Ludwig PIV V A International Civil Aviation Organization ICAO 4 2 ~ 3 min NASA 20 1 / www cnki net /kcms /detail / V html * 1961 fbao@ xmu edu cn J Bao F Liu J S Zhu R et al Control method for aircraft wake vortex based on Rayleigh-Ludwig instability J Journal of Beijing University of Aeronautics and Astronautics in Chinese 6

1382 2015 7-9 R- L DLR ONERA R-L 10 DLR F13 11-12 18 13 UCB 19 1 22 UND 20 Vor 23 14-16 15-16 16 2 24-25 17-19 2 1 Rayleigh-Ludwieg Rayleigh-Ludwig 20 R-L R-L 2 1 21 Γ 1 > 0 Γ 2

2 R- L DLR ONERA R-L 10 DLR F UCB UND 20 Vor Rayleigh-Ludwieg Rayleigh-Ludwig 20 R-L R-L Γ 1 > 0 Γ 2 < 0 Γ 1 Γ 2 Fig 1 b 1 b Classification chart of four-vortex wake system 21 a r 1 /4 2 Fig 2 Schematic of experimental model and four-vortex wake system tailored by the model

8 1383 GO436B 80 mm b = 200 mm 0 75 mm 8 981 736 1 interrogation window 16 16 25% overlap PIV 4 1 Table 1 Shapes and sizes

system for PIV measurement region 3 300 m 0 5 mm /s 45 0 4 ~ 0 5 m /s 6 ~ 15 min 10 3 98 10 4 ~ 4 95 10 4 3 2 3 PIV 3 1

b x /b PIV 45 PIV 2 2 PIV Table 2 Component parameters of PIV system Nd YAG 15 W CCD SpeedSense9040 1 600 1 200 AF VR

3 GO436B 80 mm b = 200 mm 0 75 mm interrogation window % overlap PIV 4 1 Table 1 Shapes and sizes of spoiler /mm a = /4 r = PIV Partical Image Velocimetry mm 520 mm 4 PIV Fig 4 Coordinate system for PIV measurement region m 0 5 mm /s ~ 0 5 m /s 6 ~ 15 min ~ PIV 3 1 baseline α V m /s 6 3 PIV α = 10 V = 0 5 m /s Fig 3 Xiamen university fluid dynamics and PIV laboratory 30 5 b x /b PIV 45 PIV 2 2 PIV Table 2 Component parameters of PIV system Nd YAG 15 W CCD SpeedSense AF VR Zoom-Nikkor = 80 ~ 400 mm Dynamic Studio V3 31 Al 2 O 3 = 5 μm 5 30 Fig 5 Development of primary vortex in 30 wingspans without spoiler

1384 2015 30 8 PIV Dynamicstudio ω 1 v u x y V S Г 2 A Γ i /Γ 1 i Γ i 7 Γ 1 Fig 7 Circulation variation of primary vortex

8 Development of primary vortex with spoiler 45 36 ~ 45 0 92 5 8 1 2 6 45 Fig 6 Circulation development curve of primary

4 PIV Dynamicstudio ω 1 v u x y V S Г 2 A Γ i /Γ 1 i Γ i 7 Γ 1 Fig 7 Circulation variation of primary vortex ω = v x - u 1 respecting to wingspan without spoiler y Γ L = V ds = L ωda 2 A α = 10 V = 0 5 m /s 45 Γ i /Γ Fig 8 Development of primary vortex with spoiler ~ Fig 6 Circulation development curve of primary vortex in wingspans without spoiler Γ i /Γ 1 ω R-L 16 ~ 17 R-L 45 α = 10 V = 0 5 m /s Γ i /Γ 1 10

8 1385 45 a = 50 mm 5 55 9% 21 0 42 Fig 9 Fig 10 10 45 Circulation development curve of primary vortex in 45 wingspans with spoiler α = 10 V = 0 5 m /s 45 Γ i /Γ 1 11 Fig 11 11 Circulation variation

Γ 2 / - Γ 1 η /% η - /% 0 4 8 0 4 0 406 37 30 10 0 4 0 367 36 80 a = 40 mm 6 0 4 0 414 41 30 42 0 9 0 5 8 0 4 0 373 45 80 Vortical contour of primary vortex with spoiler 10 0 4 0 376 48 60 6 0 45 0

5 a = 50 mm % Fig 9 Fig Circulation development curve of primary vortex in 45 wingspans with spoiler α = 10 V = 0 5 m /s 45 Γ i /Γ 1 11 Fig Circulation variation of primary vortex respecting to wingspan in four-vortex wake system Γ 2 / - Γ 1 η η - b 2 /b 1 1 r = 50 mm 3 3 Table 3 Relationship between parameters in four-vortex wake system V / m s α / b 2 /b 1 Γ 2 / - Γ 1 η /% η - /% a = 40 mm Vortical contour of primary vortex with spoiler a = 45 mm a = 50 mm a = 55 mm r = 50 mm

6 mm a 50 mm Γ 2 / - Γ a 55% Γ 2 / - Γ b 2 /b Γ 2 / - Γ Γ 2 / - Γ 1 η R-L a = 50 mm r = 50 mm Veillette P R Data show that U S wake-turbulence accidents are most frequent at low altitude and during approach and landing J Flight Safety Digest Holz pfel F Sensitivity analysis of the effects of aircraft and environmental parameters on aircraft eake vortex trajectories and lifetimes AIAA R Reston AIAA Fig 12 Distribution of effective parameters 5 Borer N K Barrows T M Levine D M et al Formation airdrop combinations in four-vortex wake system classification chart scaling effects on aircraft wake vortex formation and interaction AIAA R Reston AIAA Burnham D C Hallock J N Decay characteristics of wake vortices from jet transport aircraft J Journal of Aircraft % 7 Stewart E C A study of the interaction between a wake vortex 0 5 b 2 /b Γ 2 / - Γ AIAA 1993 b 2 /b 1 = 0 5 Γ 2 / - Γ PIV R-L R-L 3 R-L 10 ~ 20 4 a = r References 1 Burnham D C Hallock J N Decay characteristics of wake vortices from jet transport aircraft J Journal of Aircraft Dacles-Mariani J Hafez M Kwak D Prediction of wake-vortex flow inthenear-and intermediate-fields behind wings AIAA R Reston AIAA 1997 and an encountering airplane AIAA R Reston 8 Perry R B Hinton D A Stuever R A NASA wake vortex research for aircraft spacing AIAA R Reston AIAA Zheng Z C Xu Y Wilson D K Behaviors of vortex wake in random atmospheric turbulence J Journal of Aircraft Harris M Young R I K pp F et al Wake vortex detection and monitoring J Aerospace Science and Technology Holz pfel F Frech M Gerz T et al Aircraft wake vortex scenarios simulation package-wakescene J Aerospace Science and Technology Kauertz S Holz pfel F Kladetzke J Wake vortex encounter risk assessment for crosswind departures J Journal of Aircraft Stephan A Holz pfel F Misaka T Aircraft wake-vortex decay in ground proximity-physical mechanisms and artificial enhancement J Journal of Aircraft Rennich S C Lele S K Method for accelerating the destruction of aircraft wake vortices J Journal of Aircraft

7 8 15 Bao F Vollmers H Mattner H Experimental study on controlling wake vortex in water towing tank C Proceedings of 20th 1387 International Congress on Instrumentation in Aerospace Simula- 21 Babie B M Nelson R C An experimental investigation of bending wave instability modes in a generic four-vortex wake J 16 Robert Konrath Physics of Fluids tion Facilities Piscataway NJ IEEE Press J Quackenbush T R Boschitsch A H Bilanin A J Computational Huang S Q Shen G X Konrath R et al Experimental investiga- and experimental studies in multipair wake vortex instabilities tion of influence of jets on aircraft wake vortices J Acta Aeronautica et Astronautica Sinica in Chinese 17 Urbatzka E Wilken D Estimating runway capacities of German airports J Transportation Planning Technology Fabre D Jacquin L Stability of a four-vortex aircraft wake model J Physics of Fluids Rennich S C Lelet S K Method for accelerating the destruction of aircraft wake vortices J Journal of Aircraft Ortega J M Bristol R L Savas Experimental study of the instability of unequal-strength counter-rotating vortex pairs J Journal of Fluid Mechanics AIAA R Reston AIAA Jacquin L Fabre D Sipp D et al Instability and unsteadiness of aircraft wake vortices J Aerospace Science and Technology Rayleigh-Ludwieg J Liu Z R Zhu R Dual wingtips vortexes Rayleigh-Ludwieg instability experimental research J Journal of Experiments in Fluid Mechanics in Chinese 25 He Y Yang J W Bao F Wake vortex control using modified flaps J Applied Mechanics and Materials Control method for aircraft wake vortex based on Rayleigh-Ludwig instability BAO Feng * 1 LIU Jinsheng 1 ZHU Rui 1 JIANG Jianhua 1 WANG Junwei 2 1 School of Physics and Mechanical & Electrical Engineering Xiamen University Xiamen China 2 Jiangxi Hongdu Aviation Industry Co Ltd Nanchang China Abstract The aircraft wake vortex is an inherent flow phenomenon due to the lift generation mechanism which has a negative impact on the flight safety By adding a set of specially designed spoiler a rectangular wing was designed to generate a pair of weaker vortices which had different sizes and opposite direction compared to main wing vortices thereby constructing a self-destructive four-vortex wake system to induce Rayleigh-Ludwig instability Under different experimental conditions in terms of changing the size or shape of the spoiler towing speed and angle of attack the wake vortex development of the test model that both with and without spoiler as well as the circulation analysis were acquired particle image velocimetry PIV measurements under the low Reynolds number The study demonstrates that the decrease in circulation was 35% to 55% in 45 wingspans when spoilers are introduced whereas the counterpart of the baseline airfoil without spoilers is nearly kept steadily which reveal the application possibility of Rayleigh-Ludwig instability in alleviating the wake vortex As the initial circulation ratio equals to and the initial distance ratio is 0 5 the circulation of the primary vortex reduce most significantly 55 9% in 45 wingspans Results would provide a scheme in the design of airfoils with weaker vortices Key words aircraft wake vortex Rayleigh-Ludwig instability particle image velocimetry PIV spoiler low Reynolds number

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