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INnovative Actuation Concepts for Engine/Pylon/Wing Separation FLOw Control (Design, Build and Wind Tunnel Test)

Periodic Reporting for period 2 - INAFLOWT (INnovative Actuation Concepts for Engine/Pylon/Wing Separation FLOw Control (Design, Build and Wind Tunnel Test))

Reporting period: 2019-02-01 to 2020-09-30

Engines with high bypass ratio are more efficient than those with a smaller bypass ratio. However, the increasing nacelle diameter going along with this modification poses challenges for aircraft designers, as compliant with ground clearance regulations requires a close wing-engine coupling.
To avoid collision with the engine nacelle during take-off and landing a partial cut-back of the leading edge devices of a commercial passenger airplane wing is inevitable.
The problem being addressed in the INAFLOWT project is the local flow separation (and hence local lift reduction) due to the close coupling of the promising ultra high-bypass ratio engine to the wing and interference with its leading-edge high lift system.

This project is important to society since the local flow separation reduces the overall efficiency of the airplane in the takeoff and landing phase. On the other hand, the use of ultra-high-bypass-ratio engine is a promising way for reduction of fuel consumption and reduction of environmental footprint of air transportation.

The overall objectives of the project are to overcome the local flow separation by means of applying innovative active flow control technology. This technology, developed by the 5 teams of researchers and validated by both extensive computational fluid mechanics and two scales of wind tunnel testing at , is aimed to solve the local boundary layer separation at low energetic cost and low mass flow compared to the current state-of-the-art.

The chosen AFC method uses steady suction through a series of holes placed around the 1.5% chords location on the inboard side of the engine pylon. This location has been chosen based on CFD findings and validated experimentally in the small scale test.
Next, pulsed blowing from 4-6 span locations was added using a fluidic oscillator that is part of the SaOB actuator, placed around 12% chords of the same region. Both AFC locations were chosen to comply with existing AFC panels on the large scale model. Significant lift recovery and a certain degree of drag reduction was obtained by the efficient combination of the two AFC methods.
Comprehensive series of CFD simulations were conducted to predict the effects of steady suction and pulsed blowing alone and in combination on the large scale model.
Two scales of the SaOB actuator array were adapted, 3D printed and tested. Performance goals were met and an array was printed at TAU along with AFC panels and existing flow distribution system and sent to TSAGI for testing.
Baseline and AFC tests began at TSAGI T-101 large scale tunnel during Dec-2019. Preliminary encouraging result were obtained but after 11 runs the WT broke. Due to the Pandemic tests resumed only on Sep-21 and test plan was completed.
The final results show a good lift recovery due to the combination of steady suction and pulsed created by a six-synchronized SaOB array. The results correspond well and show superiority above to those of the AFLONEXT project, but using less that half the mass flow rate.
More importantly, the project demonstrated the capability to design, develop and apply an innovative AFC method, using two scales of wind tunnels testing, comprehensive steady and unsteady CFD and show good agreement between all components of the research project.
A series of publications has been presented in major European and world conferences and are prepared for Journal submissions.
List of objectives for the project as described in the DoA is provided herein. The achievement of which is described in brief.
1. Achieve in a small scale wind tunnel model similar flow conditions as in the baseline full scale model. Design, build and aerodynamically characterize an equivalent generic small scale baseline configuration without flow control through numerical analysis and WT test. Extensive computational studies, validated by wind tunnel data, enabled a detailed characterization of the flow topologies of the two experiments scales. The identification of similarities made it possible to investigate small scale model and to transfer the knowledge to full scale model case.
2. Overcome local flow separation using innovative AFC concept.
Design innovative actuation concepts to overcome the local flow separation. that postpone the stall angle, increase the maximum lift and the maximum L/D as the benchmark AFC technology. This task was achieved by combined computational fluid dynamics (CFD) and small scale wind tunnel testing. Numerical and experimental parametric studies were performed to further improve the efficiency of the flow control devices.
3. Improve flow physics understanding. Validation of numerical results and synergistic analysis with simplified geometry test results to improve flow physics understanding of the proposed innovative actuation concept. The data from dedicated wind tunnel tests were used for validation of CFD computational results. High level of detail was considered. Validation of CFD results allowed to adapt the numerical setup toward best compromise between computational costs and physical accuracy.
4. Reach figure of merit greater than unity for innovative AFC configuration. Optimize effectiveness while maximizing efficiency through small scale WT testing of the innovative actuation concept. Achieved in the second half of the project.
5. Provide near full-scale prototype innovative AFC hardware. Develop and manufacture hardware of the optimized actuation configuration for the large scale WT test. This is work has been performed in full.
6. Reach TRL3 with innovative AFC system. Provide an aerodynamic proof of concept (TRL 3) of the innovative AFC concept at industrially relevant flow conditions through large scale WT tests. Completed during two wind tunnel entries at TSAGI WT T-101.
7. Benchmark other AFC concepts. Benchmark and validate potential improvements gained from on-going optimization processes of matured actuators already under development in Clean Sky 2, LPA, Platform 1, through large scale WT tests. This task was not achieved due to FRANHAUFER considerations following the TSAGI T-101 WT breakdown and late repair.
The main innovation in the INAFLOWT project is the use of steady suction in addition to the already used pulsed blowing to achieve boundary layer attached flow. Steady suction is considered extremely effective flow control tool and its use significantly reduces the mass flow requirement from the pulsed blowing used further downstream.

By the end of the project it was possible to experimentally demonstrate the innovative flow control concept in large scale wind tunnel testing and, in parallel, validate the numerical approach to enable further implementation of the technique to flight tests.

The potential impacts on aviation are huge, since the concept will allow optimization of the wing design for cruise flight with the knowledge that local problems such as the currently studies local flow separation at high-lift conditions could be handled with flow control without penalizing the cruise performance.
The BFM model in TsAGI T-101 WT
Lift of the BFM using balance and sectional Cp integration
Six SaOB actuator array ready to be installed in the BFM
Sectional lift coefficient, CL, U∞ = 35 [m/s] (Re =8.8×105) using 6 suction holes and 3 PB ACTU
CFD prediction of the baseline, suction and suction and pulsed blowing effects
Surface streamlines with c_fx contour of baseline flow at α= 17° (post-stall). Negative c_fx areas i
A transparent CAD view of final BFM assembly
Time averaged streamlines entering (white) and leaving (blue) the actuator at α=17°.
Top view of wind tunnel model with pressure tap locations indicated by solid and dashed lines
Average ΔCL with respect to AoA
Wind tunnel model with AFC module inside the Knapp-Meadow wind tunnel at Tel-Aviv University
Close-up view of the AFC array module as integrated in the wind tunnel model
Installation of 6 SaOB actuators array into the BFM model