Rainer Buffo Eike Stumpf Institute of Aerospace Systems (ILR) RWTH Aachen University, Germany

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1 Rainer Buffo Eike Stumpf Institute of Aerospace Systems (ILR) RWTH Aachen University, Germany Revisiting wake vortex mitigation by means of passive devices Concept and current validation status of a novel device WakeNet-Europe Workshop 214, Paris,

2 Contents Known on-board vortex mitigation techniques Concept of VACS: Vortex Alleviation Cone System Proof of concept Current validation in the nearfield Outlook Summary Questions Slide 1

3 Known on-board vortex mitigation techniques Several devices, EU-projects AWIATOR and C-Wake [1], 26 NASA [2], 1974 Blowing at the wingtip [4], 1977 Vortex generators [4], 1977 NASA [3], 1988 Slide 2

4 Concept of Vortex Alleviation Cone System Conceptual approach Highest wv encounter during approach phase: Alleviation in this phase Modest drag is acceptable Device needs to be deployable, possibly retrofitted Simple, light, small, passive, robust, safe, independent Aerodynamic approach Momentum conservation: vortex widening for reduced intensity.1.8 [m²/s].6 Circulation Distribution in Lamb-Oseen with Different Core Widenings.12 Reference core: 3 % of b wf = wf = 2. wf = 2.5 wf = 3. wf = wf = 4. wf = 4.5 wf = 5. Core edges. c / = 71.6 % r [m] v t /U Tangential Velocity in Lamb-Oseen with Different Core Widenings.9 Reference core: 3 % of b wf = wf = 2. wf = 2.5 wf = 3..7 wf = 3.5 wf = 4..6 wf = 4.5 wf = 5. Core edges r [m] C l,ind [%] Reduction of Induced Rolling Moment on b f = b wf Slide 3

5 Concept of Vortex Alleviation Cone System Effective approach: Widening the established vortex core by w f = 2-3 using a conical tube behind the wing/flap [5] Textile / inflatable device or integrated surface U U Working mechanism Retractable wing-/ flaptip device Integrated and adaptable wing-/ flaptip feature Slide 4

6 Concept of Vortex Alleviation Cone System Physical effects: Conservation of mass Reduced axial velocity Impact on pressure drag DRAG Core widening Vorticity transport equation: ω x ω ϑ Axial velocity induction Critical Swirl Numbers: Vortex Breakdown Turbulent diffusion SAFETY Conservation of angular momentum Reduced tangential velocity SAFETY Impact on induced drag DRAG ω ϑ ω x,inlet uind ω x,outlet Vortex breakdown related to feedback- and induction-mechanism Slide 5

implementation Compartment and gearing space for installation into: Gap b/w

7 Concept of Vortex Alleviation Cone System Most intensive H/L landing flap vortex Compartment space in H/L landing configuration Realization and implementation Compartment and gearing space for installation into: Gap b/w aileron and flap Flap cavity Flap track (other a/c type) A32 wing components Slide 6

Proof of concept Preliminary investigations at RWTH Aachen using

RL22 with VC14 15 ( x c)/u 1 x/b = 18 5 2 4 6 8 1 12 14 16 18 x/b 7 %

8 Proof of concept Preliminary investigations at RWTH Aachen using generic wing-model WUK II, ILR RWTH WSK, ILR RWTH T-Canal, IWW RWTH ( x c)/u vortex axis ; = 1 x/b = x/b = 18 RL22 RL22 with VC11 RL22 with VC12 RL22 with VC13 RL22 with VC14 15 ( x c)/u 1 x/b = x/b 7 % reduction of v t,max, w f = 3 15 % reduction of c L,ind, w f = 3 Progressive reduction of ω x,max with w f Slide 7

9 Current validation in the nearfield RWTH Aachen University project funded by Innovationsfond Validation of the effectiveness and efficiency of VACS Project scope WP1: Analysis of lift, drag, effectiveness, and noise (ILR) WP2: Analysis of vortex intensity long-time development (ILR) WP 3: Analysis of air traffic benefits and solution trade-off (VIA*) WP 4: Joint workshop on expertise level (ILR & VIA*) Verkehrswissenschaftliches Institut Aachen Institute of Transport Science RWTH Aachen University Slide 8

V ~ 29 m/s Nose suction 6C Balance DMS, temperature compensated 3C PIV 4 MPx Cameras Davis by

10 Current validation in the nearfield Windtunnel and measurement configurations Flap Vortex Camera Camera Array Balance Nose Suction Flap Vortex Laser Low speed windtunnel Rec = 3. V ~ 29 m/s Nose suction 6C Balance DMS, temperature compensated 3C PIV 4 MPx Cameras Davis by LaVision PIV software 16x16 px² with 5 % overlap Acoustic Array 32 microphones Still under investigation Slide 9

Current validation in the nearfield Wing half-model

Attachment: Core capturing Hinged flaptip mounting

11 Current validation in the nearfield Wing half-model and VACS devices Articulated H/L features, BAC 3-11/RES/3/21 airfoil VACS devices with w f = 1-5 d inlet = 1 mm ~ d core l VACS = 7 mm = 4 % c mac Attachment: Core capturing Hinged flaptip mounting Cruise Take off SLAT = FLAP = 1 Landing SLAT = 2 FLAP = 2 Slide 1

Current validation in the nearfield Smoke

produce circulating breakdown region behind the

12 Current validation in the nearfield Smoke visualization, landing configuration No VACS VACS w f = 3 Indications: Increasing diffusion of vorticity with increasing w f High w f produce circulating breakdown region behind the outlet Drag penalty and effectiveness? VACS w f = 4 Slide 11

13 Current validation in the nearfield VACS influence on drag (c W ) in best L/D points 1.8 c A / c W ; Take-off Configuration ; = c A / c W ; Landing Configuration ; = ΔC L/D opt = 4 % 1 1 c A c A ΔC L/D opt = 15 %.6.4 Take Off Ref Take Off (wf=1) Take Off (wf=2) Take Off (wf=3) Take Off (wf=4) Take Off (wf=5) c W.2 Indications: Drag dominated by c W, with increasing w f c W,D increase > c W,IND reduction.4.2 Landing Ref Landing (wf=1) Landing (wf=2) Landing (wf=3) Landing (wf=4) Landing (wf=5) c W Slide 12

L/D L/D Current validation in the nearfield VACS influence on L/D 14 12 1 8 6 4 2.2.4.6.8 1 1.2 1.4 1.6 1.

14 L/D L/D Current validation in the nearfield VACS influence on L/D c A L/D over c A ; Take-off configuration ; = 2 L/D over c A ; Landing Configuration ; = 6 Landing Ref Landing (wf=1) Landing (wf=2) Landing (wf=3) Landing (wf=4) Landing (wf=5) Take Off Ref Take Off (wf=1) Take Off (wf=2) Take Off (wf=3) Take Off (wf=4) Take Off (wf=5) c A L/D [%] L/D for Take-off ( = 2 ) and Landing Configuration ( = 6 ) Take Off Take Off Fitted Curve Landing Landing Fitted Curve REF Performance degradation: Moderate for landing, excessive for take-off w f adaption for low drag service? w f Slide 13

2.15.1.5 1 2 3 4 5 Reduction of vortical motion: ω x,max : 85 %

15 Current validation in the nearfield 3C-PIV: Mitigation potential.4.35 v t,max over w f ; x/c = 5 Landing, = 6 Take-off, = v t,max Reduction of vortical motion: ω x,max : 85 % (Landing), 75 % (Take-off) v t,max : 4 % (core growth ~ 3) (both) w f Slide 14

Current validation in the nearfield v t /U.25

1 v t /U for different w f ; x/c = 5 ; Landing Ref w f = 1 w f = 2 w f = 3 w f = 4 w f = 5 q swirl 4 3.5 3 2.5 2 1.5 1.

16 Current validation in the nearfield v t /U C-PIV: Mitigation potential v t /U for different w f ; x/c = 5 ; Landing Ref w f = 1 w f = 2 w f = 3 w f = 4 w f = 5 q swirl Swirling strength over w f ; x/c = 5 Landing, = 6 Take-off, = r/s Potential for C Roll,ind reduction: Needs to be assessed for completely rolled-up vortex in the farfield Potential for swirl instability: Enhancement of turbulent diffusion? w f Slide 15

17 Outlook Further analysis: Comparing drag components from balance and 3C-PIV Assessment of swirl and turbulence Acoustic noise assessment Optimization / miniaturization / adaptivity / trade-offs Further direct project scope WP1: Analysis of lift, drag, effectiveness, and noise (ILR) WP2: Analysis of vortex intensity long-time development (ILR) WP 3: Analysis of air traffic benefits and solution trade-off (VIA*) WP 4: Joint workshop on expertise level (ILR & VIA*) Water towing tank experiments at DST** in Duisburg, Germany, Oct C-PIV, VACS at flap-tip and possibly wing-tip Start-stop investigation / mitigation 12 span vortex mitigation assessment * Verkehrswissenschaftliches Institut Aachen Institute of Transport Science RWTH Aachen University ** Development Centre for Ship Technology and Transport Systems Slide 16

18 Summary VACS Potential for hands-on vortex mitigation Generic and real-configuration tests successful Vortex mitigation For take-off: high (4 % v t,max ; 75 % ω x,max ): promising For landing: high (4 % v t,max ; 85 % ω x,max ): promising Swirl potential for turbulent diffusion behind VACS Maximum L/D penalty For take-off: high (14 w f = 5): not ok For landing: low (4 w f = 5): ok low (1 w f = 2): ok DE patent pending Slide 17

19 References [1] Wake Vortex Research Needs for Improved Wake Vortex Separation Ruling and Reduced Wake Signatures, WakeNet2-Europe, Part II Specialist s Reports FINAL, April 26 [2] Wingtip Vortex Dissipator for Aircraft, US 3,984,7, 1974 [3] Wingtip Vortex Turbine, US 4,917,332, 1988 [4] Dunham, R.: Unsuccessful Concepts for Aircraft Wake Vortex Minimization, NASA Langley Research Center, 1977 [5] Tragflügel, DE Patent pending, 213 Slide 18

20 Thank you! Questions? A project funded by the Innovation Fund of RWTH Aachen University Slide 19

A Novel Airfoil Circulation Augment Flow Control Method Using Co-Flow Jet

AIAA Paper 2004-2208, 2004 A Novel Airfoil Circulation Augment Flow Control Method Using Co-Flow Jet Ge-Cheng Zha and Craig D. Paxton Dept. of Mechanical & Aerospace Engineering University of Miami Coral