Destabilizing trailing wake vortices

Transcription

1 FarWake Workshop IRPHE Marseilles, may 2008 Destabilizing trailing wake vortices Laurent Jacquin ONERA DAFE - Meudon

2 contributors Denis Sipp, David Fabre, Vincent Brion

3 outline 1. lift 2. destabilizing aircraft wakes 3. other applications

4 high Re steady 1. aircraft

5 lift momentum cross flow momentum organizes into longitudinal vortices ω 0 1. aircraft lift

6 1. aircraft lift observations AR 1 delta wing sweep angle 60 incidence angle 30 Cz,max AR S a b 1 b a/b 1 AR = wing aspect ratio S = Swirl a/b = dipole aspect ratio for AR 1 the vortices are dissipated in the nearfield thanks to a global instability (vortex bursting)

7 1. aircraft lift A300 model C Z max =1.7 observations AR 10 x 0. 5 b x 1 b x b 5 for AR 10 the vortices are dissipated farther downstream, by local 3D instabilities b a/b << 1 Jacquin et al,, AIAA paper

8 1. aircraft lift status energy developped by lift is stored in vortices for AR 1, this energy is dissipated on place by turbulence produced after a global instability (vortex bursting) for AR >> 1, energy is dissipated in the far-field by turbulence produced after local (cooperative) instabilities. A weakly dissipative (laminar?) vortex regime precedes this final dissipation

9 outline 1. lift 2. destabilizing aircraft wakes 3. other applications

10 2. destabilizing the wake Far Wake T Task T Medium-Long-wave instability synthesis synthesis presented by Laurent Jacquin presented by Laurent Jacquin

11 Partners /Activities Task TUM 12 MM EXP 4VS genarator in wind tunnel DLR 4 MM EXP 4VS generator (F13) in large towing tank TUE 18 MM EXP/CFD Effects of turbulence on LW instabilities UCL 6 MM CFD Temporal-Spatial DNS-LES of 4VS ONERA 4 MM CFD Select a most promising 4VS by LES DLR 3 MM DLR 4 MM CFD 4VS generator (F13) with DLR code ONERA 4 MM Theory Transient growth in dipolar vortices UPM 24 MM Theory BiGlobal stability analysis of VS

12 2. destabilizing the wake case of 4 vortices outboard flaps horizontal tail plane C zmax : separation!

13 2. destabilizing the wake the optimal perturbation ( Γ Γ = ) t = 0 t = T Γ 1 Γ gain : Crow ( ) G T G T = 3 4 O ( ) ( ) Fabre, Jacquin & Loof, JFM 2002

14 destabilizing the wake Fabre, Jacquin & Loof, JFM 2002 Γ 1 Γ 2 b 2 b 1

15 1. destabilizing the wake dipole (Crow) 0 Γ Γ allowed b 2 b 1 Fabre, Jacquin & Loof, JFM 2002

16 1. destabilizing the wake Γ Γ 2 1 dipole (Crow) LW allowed Divergent Optimal perturbation Gain for τ 1 (x/b = 30) MW b 2 b 1 USW SW LW MW steady gain SW 4 < k opt b 1 < 8 ( 0.8 < λ opt b1 < 1.6) USW k optb 1 <1 1 < k opt b 1 < 4 opt ( 1.6 < λ b1 < 2π) k optb 1 < 8 opt ( λ b1 < 0.8) Fabre, Jacquin & Loof, JFM 2002

17 linear theory (τ 1, x/b = 30) 2. destabilizing the wake towing tank Savas et al. JFM 2003

18 LES of promising 4VS DLR - ONERA Optimal perturbation linear theory (τ 1, x/b = 30) LES

19 Temporal - Spatial DNS-LES of 4-vortex systems UCL LES τ = t t Crow =1.15 top view side view

20 Temporal-Spatial DNS-LES of 4-vortex systems UCL LES τ = τ = t t Crow t t Crow = 3 = 5

21 Temporal-Spatial DNS-LES of 4-vortex systems Modal energy evolution Medium (optimal) Widnall Crow UCL

22 Temporal-Spatial DNS-LES of 4-vortex systems UCL Time evolution of energy Energy is normalized using the initial energy of case -0.2

23 Temporal-Spatial DNS-LES of 4-vortex systems UCL 1.1 Time evolution of circulations half-plane total circulation

24 Temporal-Spatial DNS-LES of 4-vortex systems Time evolution of mean profiles of circulation UCL

25 x = 30 b Subtask : Medium & Long Wave instabilities LES of promising 4VS DLR - ONERA Crow-forced perturbation Gain for τ 1 (x/b = 30) Γ Γ b 2 b Crow steady gain k Crow b = 0.8 Γ1b 1 + Γ2b b = Γ + Γ 1 Note : x b = 30 Crow G =14. 5 x b = 100 Crow G = larger than 4 vortex co-rotative systems Fabre, Jacquin & Loof., JFM 2002

26 Subtask : Medium & Long Wave instabilities LES of promising 4VS Crow-forced perturbation DLR - ONERA linear theory (x/b = 30) LES DLR/ONERA red & blue = ω x white = ωθ Fabre, Jacquin & Loof JFM 2002 Stumpf, FarWake 2006

27 Awiators DLR flight tests Attas

28 Awiators DLR flight tests 4- Wirbel-System am ATTAS erzeugt (Flug über Braunschweig,, ) Klassischer Hochauftrieb sec Oszillierende DLCs gegenrotierende Wirbel, kb 1 =0.8

29 Optimal Perturbations in Dipolar Vortices ONERA Crow instability λ~8b b 45 steady Brion, Sipp, Jacquin Phys. Fluids 2007

30 Optimal Perturbations in Dipolar Vortices ONERA σ growth rate Optimisation : initialisation with the adjoint of the Crow instability Energy gain u = adjoint ue ˆ 36 σt Crow instability a/b=0.2 Re =4000 ka=0.2 time Brion, Sipp, Jacquin Phys. Fluids 2007

31 Optimal Perturbations in Dipolar Vortices ONERA Adjoint of the Crow instability

32 Optimal Perturbations in Dipolar Vortices ONERA Optimisation : initialisation with the adjoint of the Crow instability Energy gain adjoint t~ time wake collapse wake collapse Crow instability Brion, Sipp, Jacquin Phys. Fluids 2007

33 Optimal Perturbations in Dipolar Vortices ONERA 1 - Perturbation in the 2 2transport to hyperbolic 3 Stretching symmetry plane region - stretching - induction induction 4 - Crow Brion, Sipp, Jacquin Phys. Fluids 2007

34 Optimal Perturbations in Dipolar Vortices ONERA

35 outline 1. lift 2. destabilizing aircraft wakes 3. other applications

36

37 3. Other applications h/δ = 0.6 L/h = 3 '2 u + w '2 λ/h = 6 δ Gardarin, Jacquin, Geffroy, AIAA-Paper

38 Gardarin, Jacquin, Geffroy, AIAA-Paper Other applications

39 x h =1 3. Other applications VG3 VG4 VG5 VG6 VG8 drift x x x x h =1 h = 4.2 h = 6.2 h = 8.2 Gardarin, Jacquin, Geffroy, AIAA-Paper

40 v ' w ' x h = 4.2 x h = 6.2 x h = 8.2 x h = 8.2 Gardarin, Jacquin, Geffroy, AIAA-Paper Other applications

41 3. Other applications x VG4 h = 8.2 VG5 S uuu ( f ) hot wire (VG4 axis) ka =1.2 ' w ' v Nota cooperative instability short wave -5/3 λ/δ=o(1) possibly : right : short wave cooperative m=2 (swirl=0.5) or transient growth Left: turbulence macroscales forcing stable Kelvin waves m=±1 to grow transiently (following the optimal scenario, see Brion et al.) Gardarin, Jacquin, Geffroy, AIAA-Paper

42 3. Other applications short wave cooperative m=2 (swirl=0.5) or transient growth W0 = U V θ max Expé : W double U not Lacaze, Ryan & Le Dizès JFM 57

43 2. destabilizing the wake transient growth shear case of an isolated vortex Antkowiak, Brancher, PF 04 transient

44 END