Reynolds number influence on high agility aircraft vortical flows TUM-AER project proposal Outline Background and context Previous investigations Proposed ETW measurements Project aims Institute of Aerodynamics 1
Flow physics basics Large scale vortices are shed at swept wing leading-edges, strakes, etc. These vortices determine significantly lift characteristics, maneuver capabilities and stability C Lmax C L Nonlinear dependency C L (α) Stall Leading-edge system Scientific background Institute of Aerodynamics 2
Flow physics basics Vortex development depend on leading-edge sweep φ and angle of attack α α [ ] 40 35 30 25 Thin, planar wings; sharp leading edge α max 4 α 3 φ W 4: Vortex bursting over the wing 3: Span wise fixed 20 15 10 5 0 α Bursting (trailing edge) 1 α 2 α 50 55 60 65 70 75 80 85 α laminar laminar turbulent turbulent 2: Fully developed, moving inboard 1: Vortex formation φ [ ] Scientific background Institute of Aerodynamics 3
Flow physics Re influence ( ) VFE-2 (φ = 65 ) delta wing (RTO AVT-113) U M = 0.14 Re = 2.0 x 10 6 α = 13 Topology of system Laminar separation Inboard Separation Attachment Turbulent separation Primary Separation TUM-AER model c r = 0.980 m Attachment Secondary Separation Attachment Oil flow Research context Institute of Aerodynamics 4
Flow physics Re influence ( ) Ma = 0.4 (const.) Re = 1 x 10 6 Re = 2 x 10 6 Re = 3 x 10 6 URANS simulations (Courtesy W. Fritz, AIAA Paper 2008-393) Research context Institute of Aerodynamics 5
Flow physics Re influence ( ) VFE-2 delta wing M = 0.14 Re = 2.0 x 10 6 α = 13 KKK tests (T: 240 K 150 K) Ma = 0.05 0.16 Re = 1 x 10 6 6 x 10 6 α = 5 28 DLR TSP (Courtesy R. Konrath) TUM Oil flow Research context Institute of Aerodynamics 6
Flow physics Re influence Separating shear layer Vortex core (fully developed / bursting) φ Boundary layer secondary separation α = 25.0 u 2 U 0.28 U 0.20 α = 30.0 0.10 0.02 Associated characteristic instabilities φ = 76 Improving knowledge Institute of Aerodynamics 7
Flow physics Re influence ( ) 2,00 C L Ma = 0.2 1,80 1,60 1,40 1,20 Adverse trends?! Re = 2.2 x 10 6 Re = 5.6 x 10 6 Re = 10.1 x 10 6 Re Corresponding flow physics lack of knowledge high importance for performance basics for flow control mechanisms CLw 1,00 0,80 0,60 0,40 Slat: 45 Flap: 0 Tail: -15 703 713 723 C Lmax C L Nonlinear dependency C L (α) Stall Leading-edge system 0,20 0,00 α 0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 40,00 45,00 ALPHA Research context Institute of Aerodynamics 8
High Agility Aircraft Geometry 2s = 5 m, ϕ W = 45 Indices: l µ = 0.25 m, ϕ T = 45 W: Wing Λ W = 5, λ W = 0.16 T: Horiz. tail Sting 3.33 s φ W φ T 2 s Ma 0.12 Re lµ 0.7 x 10 6 7 s 1:15 scale model Previous investigations (TUM) Institute of Aerodynamics 9
- - - Technische Universität München Flow field mean axial vorticity ω x s/u Wing tip Wing leadingedge - 4.5 - -- - - - α =10 α = 10 Strake -- - - - - α =20 α = 20 - - - - Forebody α =30 Wing tip Wing leadingedge Strake Forebody α = 30 Previous investigations (TUM) Institute of Aerodynamics 10
Models cryogenic testing facilities 1:15 scale model 1:7 scale model Models (MAKO) designed for cryogenic testing focus is on 1:7 scale model availability of balance and sting Proposed ETW measurements Institute of Aerodynamics 11
Test conditions Flow parameter Ma 0.1 0.6 (load limit) Re 1 x 10 6 30 x 10 6 α 0 35 (?) (blockage) V = const; Ma & Re variable q = const; T variable β = 0 Configuration Tail-off No slat / flap setting Proposed ETW measurements Institute of Aerodynamics 12
Measured data and analysis Aerodynamic characteristics Forces and moments C L 2,00 1,80 1,60 1,40 Development stages of dominant vortices Flowfield (PIV) CLw 1,20 1,00 0,80 Re 703 713 723 0,60 0,40 0,20 C m 0,00-0,08-0,06-0,04-0,02 0,00 0,02 0,04 0,06 0,08 0,10 CPMw VFE-2 KKK (Courtesy R. Konrath) Proposed ETW measurements Institute of Aerodynamics 13
Outcome Analysis of aerodynamic characteristics and corresponding flow topologies Improving flow physics knowledge and modeling Vortical flow data base associated with significant Reynolds number variation Establishing a new test case for high-fidelity CFD applications (hybrid RANS/LES methods) This new test case would ideally extend the range of high quality data test cases currently addressed within the research activities GARTEUR AG49 and ATAAC Project aims Institute of Aerodynamics 14
Flow physics CFD challenges GARTEUR AG49: Scrutinizing Hybrid RANS/LES methods For Aerodynamic Applications VFE-2 Test case 2.2: VFE-2 delta wing ATAAC Advanced Turbulence Simulation for Aerodynamic Application Challenges u 2 U FA5 A/C Test case: ST08 Delta wing with sharp leading edge (VFE-2) Test case: AC06 Full aircraft with small aspect ratio wing (FA5) Project aims Institute of Aerodynamics 15