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AFLONEXT Report Summary

Project ID: 604013
Funded under: FP7-TRANSPORT
Country: Germany

Periodic Report Summary 3 - AFLONEXT ("2nd Generation Active Wing“ – Active Flow- Loads & Noise control on next generation wing)

Project Context and Objectives:
AFLoNext is a four-year integrated project (Level 2) of the 7th Research Framework Programme of the EU with the objective of proving and maturing highly promising flow control technologies for novel aircraft configurations to achieve a quantum leap in improving aircraft’s performance and thus reducing the environmental footprint.
WP1 - Hybrid Laminar Flow Control (HLFC) aims a highly efficient and integrated HLFC design applied on fin and wing. The main objective of this technology for the first period was on the definition of the requirements for a simplified HLFC system for the A320 VTP. The initial geometry for an outer wing of a long-range aircraft is finalized and the design of a combined suction and de-icing system which respects the space allocation requirements for the Krueger high-lift system has started.
WP2 - Active Flow Control on Airframe (AFC) targets to show the net benefit of integrated AFC for an aggressive outer wing design, based on a sound understanding of the functionality of AFC and its application on a sensitive airframe region. Furthermore the objective of this work package is to overcome the problem by actively suppressing the local flow separation linked to the wing/pylon junction by means of AFC through energizing the flow with fluidic jets. Within the first year, the main focus was on the definition of the baseline configuration to undertake numerical studies and on the integration of the actuators with regard to wing and pylon.
WP3 - Control Means for Vibration and Aeroelastic Coupling will show efficient means to mitigate vibrations on undercarriage components, to demonstrate their engineering feasibility, and to provide a validation basis for advanced numerical prediction of the associated unsteady flow fields. On the CFD (Computational Fluid Dynamics) side, the aircraft, landing gear, cavity and door geometries have been successfully cleaned-up.
The purpose of WP4, Noise Control on Airframe, is to demonstrate the noise mitigation benefit and the engineering feasibility of a porous flap side edge and mesh-type landing gear fairings by means of flight test. The target of the first period was on the definition and provision of geometries for the preparation of the CFD models regarding the investigations on the landing gear/flap interaction. The preparation for the landing gear wind tunnel test has been started and the model geometries have been specified.
The objective of WP5, Multifunctional Trailing Edge Concepts is to identify and validate the potential performance improvements and technology integration issues associated with the implementation of active trailing edge flow control technologies. 2D and 3D data from the EC project AVERT, have been taken as numerical benchmark.
AFLoNext clearly addresses the activity Greening of Air Transport in the Eco-innovation challenge set out in the work programme for aeronautics and air transport. The proposed research activity is expected to have a strong strategic impact since it contributes directly and indirectly to the development and implementation of the European policies.

Project Results:
The aim of HLFC technology is to achieve laminar flow with the help of a suction system to reduce the friction drag on the aircraft. The implementation of a suction system, however, adds additional weight, diminishing the fuel-burn benefit. The structural design of the HLFC systems for vertical tail plane and wing must be done with great care. Using the simplified suction approach originating from the ALTTA project as our guide, we plan to minimize the structure and its weight as much as possible. The application of HLFC for the fin belongs to work package 1.1, and for the wing, to WP1.2.
For the design envelope we have to distinguish between two types of flight case: first, those for which we expect the simplified suction system has to work properly, i.e. to produce laminar flow on both sides of the VTP, and, second, those with maximal loads, for which it is important to size the structural layout. The flight cases of the second type will cause deformations of the VTP box which produce high stresses at the connection of the HLFC leading edge to the front spar of the VTP box. A finite element calculation of these stresses showed that pure or grade-2-titanium can be used for manufacturing. This is beneficial, because sheets out of this material can be cold-formed, thus using manufacturing processes already planned. Cold-forming is not possible for the titanium alloy Ti6Al4V or grade-5-titanium which is most commonly used for aerospace applications.
One outcome of the PDR for the design of the HLFC leading edge was that the SONACA concept based on super plastic forming and diffusion bonding of the titanium alloy Ti6Al4V was selected for the ground-based demonstrator. The review initiated some modifications of the size and distribution of the chambers, as well as an art movement of the front spar to meet the segregation rules for the leading edge of an aircraft. Furthermore, the original system design with only one duct was changed into a design with two ducts; one for the supply of the bleed air for the wing ice protection system and a separate one for the air sucked through the micro-perforation.
Active Flow Control investigations are applied to two different but complementary design parts: the wing/pylon region when integrating modern-type High By-pass Ratio engines, and the outer region of aggressive wing-tip extension.
The WP3 for control means for vibration and aeroelastic coupling focused in the second period mainly on the ground vibration test. The ground vibration test was successfully completed. The results were needed to update the finite element model.
WP4 is divided in the activities on landing gear/flap interaction noise and the porous flap side edge investigations. The overall objectives of WP4 in the second reporting period were the design of an add-on treatment for landing gear noise reduction, wind tunnel testing of low noise landing gear devices and wind tunnel test on an Airbus-type porous flap side edge, and lastly initiating the flight test preparation and related design work for both, landing gear and flap side edge.
Multifunctional trailing edge concepts objectives are to investigate trailing-edge flow control devices that are multi-functional i.e. those that can be used at low and high speed and/or for the control of different aerodynamic phenomenon, the use of numerical analysis to study the potential aerodynamic benefits of a variety of trailing-edge devices, such as fluidic Gurney flaps, and therefore determine the key design and performance requirements of such devices.

Potential Impact:
AFLoNext exploitation of results of the TS1 are design and structural testing of a fully integrated wing leading edge section featuring advanced HLFC technology with focus on an innovative wing ice protection system (WIPS), Krueger flap linkage system, collapsible carbon fibre reinforced plastics (CFRP) Krueger panel with folding bull nose and the assessment of attachment line transition (ALT) device. Furthermore, engineering feasibility of advanced HLFC technology applied on fin proven by means of prototype demonstration in operational environment is the other expected result of TS1.
An experimental demonstration of locally applied active flow control technologies for performance increase and/or loads control is the expected result from TS2 and TS3.
Besides the mentioned results, the engineering feasibility of noise and vibrations mitigation technologies proven by means of prototype demonstration in operational environment is among the expected results. This focuses on design improvement and analysis from dynamic point of view (transient and aeroelastic response), improvement of landing gear doors manufacturing process (new materials, new design principles) and porous flap side edge (PFSE) for airframe noise reduction.
Further, the Assessment of novel trailing edge flow control concepts counts to the main expected results of TS4.
AFLoNext clearly addresses the activity Greening of Air Transport in the Eco-innovation challenge set out in the work programme for aeronautics and air transport. The proposed research activity is expected to have a strong strategic impact since it contributes directly and indirectly to the development and implementation of the European policies, namely competitiveness of aeronautics’ market - Knowledge and economic development and solving social problems like environmental impact, quality of life of European citizens, impact on employment, impact on employee’s skills and working conditions and of course safety issues.

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