TY - GEN
T1 - Investigation of Transition and its Active Control in Separation Bubbles for a Wing Section at Re=200k
T2 - AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022
AU - Hosseinverdi, Shirzad
AU - Guerra, Adrián Grille
AU - Fasel, Hermann F.
AU - Little, Jesse C.
N1 - Publisher Copyright:
© 2022, American Institute of Aeronautics and Astronautics Inc.. All rights reserved.
PY - 2022
Y1 - 2022
N2 - The fundamental flow physics of transition in uncontrolled and controlled separation bubbles for a modified NACA 643 − 618 airfoil at a chord Reynolds number of Re = 2 × 105 is investigated using a combined approach consisting of high-fidelity direct numerical simulations, linear stability analysis, and high-quality wind-tunnel experiments. For the uncontrolled flow, results from the DNS indicate a mean separation bubble that is larger than in the experiments, which may be explained by an earlier transition onset in the experiments caused by free-stream turbulence. In addition, active control of the laminar separation bubbles was investigated. Active flow control in the DNS is achieved by 2-D harmonic blowing and suction through a narrow spanwise slot, while the experiments use an alternating current dielectric barrier discharge plasma actuator. In both cases, the intent is to generate periodic 2-D disturbances upstream of the separation location. For the controlled flow, when forced with relatively small amplitudes, both experiment and DNS exhibit 3-D disturbance waves with distinct spanwise periodic structures that are generated inside the bubble near the maximum bubble height. Without additional (i.e., random) perturbations in the DNS (except the 2-D disturbances used for flow control), a delay of transition and even re-laminarization of the flow is demonstrated. By comparison of the DNS results with experimental data and stability theory, the dominant physical mechanisms for both the controlled and uncontrolled flows are identified.
AB - The fundamental flow physics of transition in uncontrolled and controlled separation bubbles for a modified NACA 643 − 618 airfoil at a chord Reynolds number of Re = 2 × 105 is investigated using a combined approach consisting of high-fidelity direct numerical simulations, linear stability analysis, and high-quality wind-tunnel experiments. For the uncontrolled flow, results from the DNS indicate a mean separation bubble that is larger than in the experiments, which may be explained by an earlier transition onset in the experiments caused by free-stream turbulence. In addition, active control of the laminar separation bubbles was investigated. Active flow control in the DNS is achieved by 2-D harmonic blowing and suction through a narrow spanwise slot, while the experiments use an alternating current dielectric barrier discharge plasma actuator. In both cases, the intent is to generate periodic 2-D disturbances upstream of the separation location. For the controlled flow, when forced with relatively small amplitudes, both experiment and DNS exhibit 3-D disturbance waves with distinct spanwise periodic structures that are generated inside the bubble near the maximum bubble height. Without additional (i.e., random) perturbations in the DNS (except the 2-D disturbances used for flow control), a delay of transition and even re-laminarization of the flow is demonstrated. By comparison of the DNS results with experimental data and stability theory, the dominant physical mechanisms for both the controlled and uncontrolled flows are identified.
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U2 - 10.2514/6.2022-2329
DO - 10.2514/6.2022-2329
M3 - Conference contribution
AN - SCOPUS:85123886509
SN - 9781624106316
T3 - AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022
BT - AIAA SciTech Forum 2022
PB - American Institute of Aeronautics and Astronautics Inc, AIAA
Y2 - 3 January 2022 through 7 January 2022
ER -