No SBVGs With SBVGs AWIATOR Project Perspectives: Passive Flow Control on Civil Aircraft Flaps using Sub-Boundary Layer Vortex Generators David Sawyers Aerodynamics R&T Co-ordinator Airbus UK Limited KATnet II Separation Control Workshop - 01-03 April 2008
Presentation Overview Background Passive Flow Control for High Lift Applications What are SBVGs and how do they work? Potential Benefits of using SBVGs on Trailing Edge Flaps Previous Work on SBVG design SBVGs in the AWIATOR Programme SBVG Design Wind Tunnel Testing Flight Testing Concluding Remarks KATnet II Separation Control Workshop - 01-03 April 2008 Page 2
Background KATnet II Separation Control Workshop - 01-03 April 2008 Page 3
Passive Flow Control for High Lift Applications Motivation Extended ranges for civil aircraft means that the take-off and landing performance (low speed) is a critical factor in design. Conventional ways to Improve Low Speed Performance Increase the wing area (potentially increased drag & reduced range). Design a more mechanically complex high-lift system (increased weight). KATnet II Separation Control Workshop - 01-03 April 2008 Page 4
Passive Flow Control for High Lift Applications The use of Simple (Passive) Flow Control Devices Increases the efficiency of high lift systems whilst maintaining simplicity. High lift performance is limited by boundary layer separations. Two approaches to reduce separation: (1) careful optimisation of flap gap (Ÿ increased gap sensitivity, more difficult to manufacture within tolerances) (2) limit flap angle (Ÿ loss in potential performance CLmax) Sub Boundary-layer Vortex Generators (SBVGs): (1) Reduce flow sensitivity to flap gap. (2) Re-attach separated flow for high flap angles without incurring a large drag penalty at cruise and take-off. KATnet II Separation Control Workshop - 01-03 April 2008 Page 5
SBVGs What are they? Surface mounted vortex generators where the VG height < BL height How they work? These SBVG s control the flap boundary layer by adding momentum to the boundary layer, at the flap surface. By doing so SBVG s control (delay) the boundary layer separation. These SBVGs are mounted on the flap upper surface so that they delay flap boundary layer separation only when the flap is deployed. When the flap is stowed, the SBVG s are contained in the cove region, under the shroud. Vortex Influence Paths Direction of onset flow SBVG on Flap KATnet II Separation Control Workshop - 01-03 April 2008 Page 6 h
Potential Benefits of SBVGs on Flaps Existing Aircraft Application (i.e. as a retrofit) Increase CL At high flap angles the flap becomes separated but SBVGs can re-attach the flap and allow the a/c to cash in the benefit of increased lift from the increased flap angle. potential to decrease approach speed and hence approach noise Decrease Sensitivity to Gap (risk mitigation) Can be used at take-off or landing to reduce separations due to flap gap geometry sensitivity. Increase Drag at Landing Increasing the flap angle will have a drag increase without any loss in CL max which may be favourable in cases where the option of a steep approach would be beneficial. Higher flap angle KATnet II Separation Control Workshop - 01-03 April 2008 Page 7 C L C L D With SBVGs D
Potential Benefits of SBVGs on Flaps New Aircraft Design New a/c variant that requires higher CL, can use SBVGs to achieve higher flap angles without having to go to a complex system Design a simplified high lift system with a smaller flap at higher angles (reduce weight and complexity) but give the same landing and take-off performance. KATnet II Separation Control Workshop - 01-03 April 2008 Page 8
Previous Work National High-Lift research programmes with Airbus & QinetiQ examined SBVG designs (shape, size, angle) in a simple 2D BL test. (CARAD) Looked at different SBVG designs and their effectiveness for more complex applications. (NEXUS) 5 0 Boundary-layer Testing -2000.00-1595.96-1191.92-787.88-383.84 20.20 15 10 x/h Full complex configuration, at high Re No. (6m) (2001) KATnet II Separation Control Workshop - 01-03 April 2008 Page 9
SBVGs in AWIATOR KATnet II Separation Control Workshop - 01-03 April 2008 Page 10
SBVGs in AWIATOR AWIATOR (Aircraft WIng with Advanced Technology OpeRation) The aim of this project was to contribute to new future aircraft designs by applying and integrating new technologies. (CEC FP5) Demonstration by various flight tests on an A340 after having first been simulated using a number of computational methods and validated in wind tunnel and other aircraft ground tests. Objectives of SBVG task (T3.4) To demonstrate technologies for improving the performance of trailing edge flap systems using simple flow control devices. To demonstrate if SBVGs can be used to: increase the trailing edge flap angle 32 to 35 by doing this increase CL throughout the incidence range without incurring a loss in L/D for take-off. Phases Phase 1: SBVG Design Phase 2: Wind Tunnel Testing Phase 3: Flight Testing KATnet II Separation Control Workshop - 01-03 April 2008 Page 11
SBVG Design CFD study (ONERA) Structured mesh Navier-Stokes calculations (elsa code) Data on the sensitivity of the flap boundary layer to Reynolds Number. Experimental pressure data was used to validate the CFD for the baseline and finally complex CFD calculations with SBVG representation was also used to refine the final SBVG design. BL Calc (QQ) Using the CFD calculations as an input boundary layer calculations were performed CALLISTO code Scaled SBVGs for the boundary layer of the aircraft. Output The output of this collaborated design work was a baseline array of SBVGs, which was taken forward to be optimised and demonstrated in a series of wind tunnel tests. F1 Wind Tunnel Test KATnet II Separation Control Workshop - 01-03 April 2008 Page 12 CFD
Wind Tunnel Testing KATnet II Separation Control Workshop - 01-03 April 2008 Page 13
Wind Tunnel Testing Overview Model A340 high-lift half model Model scale 1:14.4 Tunnel Entries Entry 1: Airbus LS Tunnel, Filton June 2004 Atmospheric (Re=2.2m) ID optimum SBVG arrangement Entry 2: ONERA F1 Tunnel July 2004 Pressurised to 3bar (Re=6.6m) Examine Re effects Measurements Forces & Oil flow visualisations KATnet II Separation Control Workshop - 01-03 April 2008 Page 14
Wind Tunnel Testing Airbus FLSWT Test Objective: To assist in determining the optimum SBVG arrangement to be fitted to the flaps for the AWIATOR test flight to allow an increased trailing edge flap deflection angle with acceptable flow quality. Main Observations: The optimised SBVG array significantly reduced the extent of boundary layer separation of the flap at an increased flap deflection of Gf = 35. The addition of SBVGs to the flap at Gf = 35 deflection increased the lift coefficient by up to 2.2% over a wide incidence range compared to the baseline configuration of Gf = 32 without SBVGs. The effect of SBVGs at a fixed landing flap deflection increased the lift coefficient by 'CL = 0.01 to 0.04 over part of the incidence range indicating, as expected, that the vast majority of the lift increase is due to increase in flap angle. A trend to a small increase in drag of 4 counts (Cd=0.0004) in takeoff configuration is within the repeatability of the wind tunnel balance and therefore deemed not significant. KATnet II Separation Control Workshop - 01-03 April 2008 Page 15
Wind Tunnel Testing Airbus FLSWT Results No SBVGs No SBVGs No SBVGs With SBVGs With SBVGs With SBVGs KATnet II Separation Control Workshop - 01-03 April 2008 Page 16
Wind Tunnel Testing ONERA F1 Test Objective: To investigate Reynolds number effects on the optimised SBVG array as defined in the Airbus LSWT test (Filton). Main Observations: Good correspondence of CL-alpha curves and drag increments was observed between FLSWT and F1. At high Reynolds number (Re=6.6m) the optimised SBVG array from the Filton test (ref height of h1) significantly reduced the extent of boundary layer separation of the flap at an increased flap deflection of Gf = 35, see Figure. With an increase in Re the incidence range of CL improvements due to higher flap deflection and SBVG application is extended, see Figure. At Re=6.6 the level of CL improvement at a reference alpha (approx 0.8 CLmax SBVGs off) is slightly larger (2.25%) than at atmospheric conditions (Re=2.2m) SBVGs of smaller heights (h2 and h3) could not cure flap flow separation at the highest Reynolds number. With higher Reynolds numbers a drag increase in take-off configuration due to SBVGs installation at atmospheric pressure is not observed outside the tolerance of the balance. KATnet II Separation Control Workshop - 01-03 April 2008 Page 17
Wind Tunnel Testing ONERA F1 Results No SBVGs No SBVGs With SBVGs With SBVGs KATnet II Separation Control Workshop - 01-03 April 2008 Page 18
Wind Tunnel Testing ONERA F1 Results Run 865, df=35, Re=2.2E6, SR1opt Run 591, df=35, Re=6.6E6, SR1opt AWIATOR 3.4 SBVG LSWT Test Modell 419B, G s =19.6 /23 /23, G f =32, 35 Ma=0.2, Re=2.2x10 6, 6.6x10 6 Gf=35q with SBVGs (Re=6.6m) Reference Data Run 524, df=32, Re=2.2E6, no SBVGs Run 702, df=32, Re=6.6E6, no SBVGs Gf=35q with SBVGs (Re=2.2m) Increase in CL of 2.25% at ref alpha Delta CL Gf=32q no SBVGs Alpha X:\A erodynamic s\b61\hlwd\k arsten\awiator\onera F1\OneraF1_FLSWT_forces_prel_datasorted_0721z.exy SB VG Improvement Potential DCLa V2 KATnet II Separation Control Workshop - 01-03 April 2008 Page 19
Flight Testing KATnet II Separation Control Workshop - 01-03 April 2008 Page 20
Flight Testing - Overview Main Objective: To demonstrate, on a full scale-aircraft, that SBVGs can be used to increase the trailing edge flap angle beyond the current maximum whilst maintaining attached flow. This would release an additional lift increment whilst minimising any increase in buffeting. Tests Completed: The optimised SBVG arrangement as identified from wind tunnel testing was tested at aircraft scale on the A340-300 MSN 1 flight test aircraft. The aircraft was tested at stall and climb performance conditions with and without SBVGs installed to allow a full comparison of results. KATnet II Separation Control Workshop - 01-03 April 2008 Page 21
Flight Testing Aircraft Modifications Modification of the flap kinematics Mechanism changes to allow flaps to deploy to 35 New rear links as detailed Flap System Adaptor wire installed on MSN1 Spoiler extension on spoilers 3-5 Mounting of SBVGs on the flaps Design & Manufacture SBVGs cut out of aluminium strips Mounting of SBVGs Strips mounted across full span of I/B & O/B flap Mounted using speed tape KATnet II Separation Control Workshop - 01-03 April 2008 Page 22
Flight Testing Flight Test Instrumentation Flight Test Instrumentation Lift and drag measurements (Onboard) Pressure measurements Slat-wing-flap (1 station) Flap (additional station) Flap deformation measurements (EDT) 2 stations with stereo arrangement (DLR) wing pressure measurement flap deformation measurement (EDT) Flow cones & cameras On the slats 3/4, wing & flap Indication of Tail Plane buffeting Accelerometer mounted on HTP KATnet II Separation Control Workshop - 01-03 April 2008 Page 23
Flight Testing Main Observations Flap Flow Behaviour Flow cones indicated improvement in flap flow with SBVGs on at 35. Flap flow at 35 without SBVGs was not as separated in 2005 as expected from previous experience. The flow behaviour observed on the wing with the SBVGs installed was more noticeably improved for the flap at 35 than with the flap at 32. At 35 there is no clear improvement on the inboard flap as it remains largely separated. On the outboard flap there is improvement whatever alpha. CL-Alpha Plots 32-35 CL-alpha trend is as expected, increase in CL of approx 2.5% at reference alpha. CL increase across the range but 35 stall is 0.3 degree early. KATnet II Separation Control Workshop - 01-03 April 2008 Page 24
Concluding Remarks This work has demonstrated, at aircraft scale, that by reducing flap flow separation SBVGs can be used to enable low speed improvements associated with increased flap angle to be exploited on civil aircraft. The increase in flap angle leads to an increase in lift that can be exploited in landing across the CL range without incurring a significant drag penalty in take-off. SBVGs provide a simple, effective, innovative means of enabling the increase of the performance of an existing under-performing flap system with imposing any significant weight, complexity, cost penalty. SBVGs have the future potential to adopt a simpler, lighter, cheaper flap system to give a similar performance by exploiting the following characteristics: Same lift despite non-optimum flap gap geometry Allow an increase in the maximum flap deployment angle KATnet II Separation Control Workshop - 01-03 April 2008 Page 25
Thanks any Questions? KATnet II Separation Control Workshop - 01-03 April 2008 Page 26
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