Investigating the impact of coupled high-lift devices on natural laminar flow airfoils

Colletti, Christopher Robert

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https://hdl.handle.net/2142/120285 Copy

Description

Title

Investigating the impact of coupled high-lift devices on natural laminar flow airfoils

Author(s)

Colletti, Christopher Robert

Issue Date

2023-04-21

Director of Research (if dissertation) or Advisor (if thesis)

Ansell, Phillip J

Doctoral Committee Chair(s)

Ansell, Phillip J

Committee Member(s)

• Chamorro, Leonardo
• Saxton-Fox, Theresa A
• Merret, Jason M
• Shmilovich, Arvin

Department of Study

Aerospace Engineering

Discipline

Aerospace Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• aerospace engineering
• applied aerodynamics
• high-lift devices
• natural laminar flow
• active flow control
• fluidic oscillators
• morphed leading edge
• morphed geometry
• genetic algorithm
• wind tunnel
• experimental
• OVERFLOW
• MSES
• airfoil
• stereo-PIV
• oil flow visualization

Abstract

A set of experiments were conducted on the S207 airfoil at the University of Illinois at Urbana-Champaign in order to study the influence of coupled high-lift devices on the performance of a natural laminar flow airfoil in high-lift conditions, such as takeoff and landing. Both computational and experimental analyses were used to characterize the influence of three different high-lift devices, morphed leading edges, aft element deflection, and active flow control through embedded fluidic oscillators. A genetic algorithm was developed to design a set of blunted and drooped leading edge geometries, using MSES to evaluate the performance of the morphed geometries. Additionally, OVERFLOW was used to perform a sensitivity analysis on the placement and frequency of the fluidic oscillators embedded into the slotted natural laminar flow airfoil. A series of four wind tunnel experiments were used to validate the computational results and further investigate the influence of the coupled high-lift devices on the on- and off-body flow field. Testing of the model was performed at =1.210^6 and =1.410^6. Surface pressure force data was collected across four sets of experiments. The first three experiments individually focused on analyzing the three different high-lift devices, morphed leading edges, aft element deflection, and active flow control, at =1.410^6. The fourth experiment focused on evaluating the performance of select configurations at =1.210^6. Results from these experiments were used to select configurations of interest to further investigate with stereo-PIV and oil flow visualization. Stereo-PIV data were collected at =1.410^6 and focused on four configurations near stall to investigate the influence of the coupled high-lift devices on the off-body flow structures forming over the upper surface of the aft element. Oil flow visualization was run at =1.210^6 and images were taken for four configurations pre- and post-stall to further characterize the influence of the three coupled high-lift devices. Morphed leading edges were identified as a viable alternative to more common leading edge devices, such as a Krueger flap or leading edge slat. The genetic algorithm was able to generate multiple viable morphed geometries and the performance of the geometries were experimentally validated. Each morphed geometry led to an increase of Δ,=0.5−0.7 compared to the baseline geometry. Drooping the leading edge was found to have a larger influence on the lift of the airfoil, while blunting the leading edge was found to have a larger influence on the boundary layer health. The combination of blunting and drooping the leading edge led to a morphed geometry that both improved the performance of the airfoil and generated a more favorable pressure gradient along the leading edge compared to the standard geometry. This changed the stall behavior of the slotted natural laminar flow airfoil from a leading edge stall to a trailing edge stall. Aft element deflection further increased the performance of the S207 airfoil, leading to ,3 when coupled with morphed leading edge geometries. Lift increased as the aft element was deflected to 15°, but diminishing returns were observed at higher deflections. As the aft element was deflected, regions of separation were observed to form on the upper surface of the aft element. Active flow control elements were embedded into the aft element and the internal geometry of the fluidic oscillators were sized to produce a frequency that targets shear layer instabilities in the flow. Oscillatory actuation was observed to reduce separation on the aft element, reduce the size of the airfoil wake, and slightly increase the lift of the airfoil. In the ranges tested, up to =1.0, no diminishing effectiveness of active flow control from the fluidic oscillators was observed. Embedded fluidic oscillators were found to produce a similar improvement in performance as that of a simple flap on the aft element.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Christopher R. Colletti

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