- Vortex Interactions with Wakes - Wing elements, fuselage, and landing gear

Transcription

1 - Vortex Interactions with Wakes -, fuselage, and landing gear Ulrich Jung, Christian Breitsamter Introduction Experimental technique Results and Analysis Fuselage Landing gear Conclusions / Prospects 1

2 Problem task wake vortex alleviation Low Vorticity Vortex (LVV): Reduction of peak vorticity by enhanced dispersion of vorticity field Quickly Decaying Vortex (QDV): Excitation of inherent threedimensional wake vortex instabilities Γ/ Γ 0 1 Turbulent diffusion Rapid decay (Ortega et al., Berkely) T* QDV T* t* Increased core diameter Reduced swirl velocity Analysis of turbulent flow fields and unsteady effects 2

3 Problem task wake vortex alleviation Low Vorticity Vortex (LVV) passive configuration elements Turbulence inducing elements (viscous effects) Flap elements Spoiler / delta spoiler (DLR) (V. Rossow) Vortex inducing elements (convective effects) Wing fins Segmented flap configurations Differential flap setting (DFS) 3

4 Problem task wake vortex alleviation Basis: Fundamental investigation on the influence of wing elements on the wake vortex evolution and development 4

5 Introduction Experimental technique Results and Analysis Fuselage Landing gear Conclusions / Prospects 5

6 Experimental technique Laser scanning of the TAK model high lift configuration Design and fabrication of a landing gear for the TAK model Wind tunnel measurements on Winglet Nacelles on Fuselage wake Fuselage Winglet vs. wing tip Nacelles on vs. nacelles off Wing tip Nacelles off 6

7 Experimental technique High lift configuration C L = 1.43 Half model (TAK) of a Large Transport Aircraft Slats (i/b, m/b, o/b): 19.6, 23.0, 23.0 Flaps (i/b, o/b); Aileron: 26.0, 26.0 ; 5.0 Horizontal tail plane: -6.0 ; Angle of attack: 7.0 l μ Peniche b/2 ±Z ±Y ±X Traverse system Geometry Model scale: 1:19.25 Wing half span b/2: m Aspect ratio Λ: 9.5 Test section: 1.8m x 2.7m x 21m Triple-wire probe 7

8 Wind tunnel facility m/s x/b

9 Flow field measurements hot-wire anemometry E 3 [ V] 1.25 mm Triple-wire probe θ C θ c,max φ C φ c U C E 1 [ V] E 2 [ V] Velocity and flow angle dependent calibration Refined calibration surfaces (look-up table) 9

10 Experimental technique Flow and data acquisition parameters: Free stream velocity Reynolds number U 6 Re 10 l μ [m/s] [ - ] U Sampling rate f M 3000 [Hz] Low pass filter f T 1000 [Hz] Sampling interval t M 6.4 [ s ] Analyzed dimensionless quantities: Axial vorticity: Turbulence intensity: ξ = b 2 U Tu z = w y v z w 2 U Flow visualization No separation on wing and control surfaces 10

11 Introduction Experimental technique Results and Analysis Fuselage Landing gear Conclusions / Prospects 11

12 Results Fuselage wake Vorticity Turbulence intensity x/b = 0.20 x/b = 0.37 Vortex due to inclined fuselage Belly fairing vortex Tail cone vortex - negative vorticity x/b = 0.20 x/b = 0.37 Vorticity areas / boundary layer are indicated by increased turbulence intensities 12

13 Results Fuselage wake: CFD - Exp ARGO ARGO (CENAERO) (CENAERO) (TUM) RANS DES Far better agreement with experimental results using DES Limitated dissipation of vortex cores Pretty good qualitative & quantitative prediction of the wake vorticity pattern emanating from the fuselage 13

14 Results Fuselage wake Most prominent effect for the wing-fuselage configuration in the fuselage area is the wingfuselage vortex (!) (negative circulation gradient) Vorticity Fuselage wake Wing- Fuselage vortex x/b =

15 Introduction Experimental technique Results and Analysis Fuselage Landing gear Conclusions / Prospects 15

16 Results WTV: Wing Tip Vortex OFV: Outboard Flap Vortex ONV: Outboard Nacelle Vortex INV: Inboard Nacelle Vortex WFV: Wing Fuselage Vortex x/b = 0.37 WTV ONV OFV HTV INV WFV U HTV: Horizontal Tailplane Vortex Axial vorticity / geometric discontinuities 16

17 Results numerical analysis Reynolds Number Effect Picture: Vortices of High Reynolds number case in red, Low Reynolds number case in blue Main changes on inboard section: additional vortices / change of position at higher Reynolds number Outboard wing: nearly unchanged 17

18 Results winglet vs. wing tip Winglet Wing tip The dominant vortices rotate INV ONV OFV WTV x/b = 0.37 INV ONV OFV WTV (counter-clockwise) around the roll-up center (center of free circulation ~ merged OFV- ONV) to form a single vortex There is no main difference in the vortex topology between wing tip and winglet configuration WTV OFV- ONV WTV OFV- ONV The wing tip configuration exhibits higher vorticity peaks INV x/b = 3.00 INV Axial vorticity 18

19 Results nacelles on/off Nacelles on Wing tip vortex x/b = 0.37 Inboard and outboard nacelle vortices Wing tip vortex Outboard flap vortex Wing tip vortex Nacelles off x/b = 3.00 Inboard nacelle vortex Merged outboard flap and outboard nacelle vortex Outboard flap vortex Axial vorticity 19

20 Introduction Experimental technique Results and Analysis Fuselage Landing gear Conclusions / Prospects 20

21 Results Landing gear x/b = 0.02 Cross flow velocity Axial vorticity 21

22 Results Landing gear Numerical simulation of isolated landing gear (DLR) Objective: Analysis of the vortex topology Grid refinement by grid adaptation 22

23 Results Landing gear x/b = 0.02 Turbulence caused by i/b nacelle Turbulence caused by o/b nacelle Area of increased turbulence intensity due to landing gear wake Quadruple structure due to landing gear vortex Turbulence intensity Turbulent shear stress 23

24 Baseline Landing gear conf. The landing gear produces the weak Landing Gear Vortex Axial vorticity No significant changes of the wake structure apart from the Landing Gear Vortex x/b = 0.37 Area of increased turbulence intensity due to landing gear wake Turbulence intensity 24

25 Baseline Landing gear conf. Counter clockwise rotation of the vortices Shear layer rolling up into HTV Increased turbulence intensities at the position of the vortices x/b = 1.00 No significant changes apart from the turbulence bubble, which is still visible 25

26 Spectral analysis f Crow 1 2 Hz f Crouch 5 20 Hz x/b = 0.02 Landing gear conf. landing gear stay f d = 250 Hz 275 Hz lateral extension of wheel pair f D = 48 Hz 53 Hz vertical extension of inclined wheels f h = 37 Hz 40 Hz 26

27 Spectral analysis Landing gear conf. x/b = 0.37 The spectra exhibit broadband characteristics the distributions of which are in general similar to those of the wing vortex sheet 27

28 Introduction Experimental technique Results and Analysis Fuselage Landing gear Conclusions / Prospects 28

29 Conclusions The influence of fuselage and wing elements on the wake vortex evolution and development has been studied The fuselage wake consists of 3 vortices: inclined fuselage, belly fairing, tail cone vortex; the fuselage turbulent wake enhances the diffusion of (counter-rotating) inboard vortices (hampering the persistence of fast decaying 4-vortex systems) The structure of the final rolled-up vortex in the extended near field is only little influenced by nacelle and wing tip vortices in the present case The deployed landing gear produces a weak landing gear vortex and a strong turbulent wake influencing the inboard vortex sheet and shifting the main vortex centers slightly outboard in the near field. Narrow-band concentrations of turbulent energy due to the periodic vortex shedding at the landing gear are weak. Wake instabilities are not excited. 29