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Aerospace 2018, 5(4), 114; https://doi.org/10.3390/aerospace5040114

Active Control of Laminar Separation: Simulations, Wind Tunnel, and Free-Flight Experiments

1,†,* and 2,†
1
Mechanical and Aerospace Engineering Department, New Mexico State University, Las Cruces, NM 88003, USA
2
Aerospace and Mechanical Engineering Department, University of Arizona, Tucson, AZ 85721, USA
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Received: 21 September 2018 / Revised: 24 October 2018 / Accepted: 26 October 2018 / Published: 30 October 2018
(This article belongs to the Special Issue Design and Analysis of Wind-Tunnel Models and Fluidic Measurements)

Abstract

When a laminar boundary layer is subjected to an adverse pressure gradient, laminar separation bubbles can occur. At low Reynolds numbers, the bubble size can be substantial, and the aerodynamic performance can be reduced considerably. At higher Reynolds numbers, the bubble bursting can determine the stall characteristics. For either setting, an active control that suppresses or delays laminar separation is desirable. A combined numerical and experimental approach was taken for investigating active flow control and its interplay with separation and transition for laminar separation bubbles for chord-based Reynolds numbers of Re ≈ 64,200–320,000. Experiments were carried out both in the wind tunnel and in free flight using an instrumented 1:5 scale model of the Aeromot 200S, which has a modified NACA 643-618 airfoil. The same airfoil was also used in the simulations and wind tunnel experiments. For a wide angle of attack range below stall, the flow separates laminar from the suction surface. Separation control via a dielectric barrier discharge plasma actuator and unsteady blowing through holes were investigated. For a properly chosen actuation amplitude and frequency, the Kelvin–Helmholtz instability results in strong disturbance amplification and a “roll-up” of the separated shear layer. As a result, an efficient and effective laminar separation control is realized. View Full-Text
Keywords: laminar separation bubble; active flow control; separation control; wing section simulations; wind tunnel experiments; free-flight tests laminar separation bubble; active flow control; separation control; wing section simulations; wind tunnel experiments; free-flight tests
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Gross, A.; Fasel, H.F. Active Control of Laminar Separation: Simulations, Wind Tunnel, and Free-Flight Experiments. Aerospace 2018, 5, 114.

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