Closed-loop control of a turbulent wake by Dielectric Barrier Discharge (DBD)

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1 Journées du GDR "Controle Des Décollements", Ecole centrale, Lyon, 28/11/2016 Closed-loop control of a turbulent wake by Dielectric Barrier Discharge (DBD) V. Parezanovic, Y. Bury and L. Joly ISAE-SUPAERO, Toulouse 1

2 In the context of project «CARPE»... Project motivation: - CARPE: Robust control of flow behind a thick plate (Contrôle Actif Robuste d écoulement de Plaque Epaisse) - Reduction of drag by closed-loop control - Control of a bluff cylinder wake, ie. von Karman vortex street - Closing the loop to obtain robustness Experimental study goals: - Working closed-loop control prototype - Detailed flow study (actuator physics, wake dynamics, different configurations, etc...) - Implementation of a model-based controller (with IMT, Toulouse)

3 In the context of project «CARPE»... Project motivation: - CARPE: Robust control of flow behind a thick plate - Reduction of drag by closed-loop control - Control of a bluff cylinder wake, ie. von Karman vortex street - Closing the loop to obtain robustness Experimental study goals: - Working closed-loop control prototype - Detailed flow study (actuator physics, wake dynamics, different configurations, etc...) - Implementation of a model-based controller (with IMT, Toulouse)

4 Wake stabilization at low Re Steady disturbance control (small control cylinder) Complete vortex shedding extinction at Re=46 with D/d=10 P. J. Strykowski and K. R. Sreenivasan, (1990) 4

5 Profile drag of a 2D bluff body Parezanovic, V. & Cadot, O. (2012). Experimental sensitivity analysis of the global properties of a two-dimensional turbulent wake. Journal of Fluid Mechanics, 693,

Closed-loop control Feedback control / direct wake control / primary instability / synchronisation Pastoor, M., Henning, L., Noack, B. R., King, R., & Tadmor, G. (2008).

6 Closed-loop control Feedback control / direct wake control / primary instability / synchronisation Pastoor, M., Henning, L., Noack, B. R., King, R., & Tadmor, G. (2008). Feedback shear layer control for bluff body drag reduction. Journal of Fluid Mechanics, 608(7), Stalnov, O., Fono, I., & Seifert, A. (2011). Closed-loop bluff-body wake stabilization via fluidic excitation. Theoretical and Computational Fluid Dynamics, 25(1-4),

Control of the secondary wake instability Active or passive / steady perturbation / secondary instability / reducing 2D flow ordering Park, H., Lee, D., Jeon, W. P., Hahn, S., Kim, J., Kim, J.,... & Choi, H.

7 Control of the secondary wake instability Active or passive / steady perturbation / secondary instability / reducing 2D flow ordering Park, H., Lee, D., Jeon, W. P., Hahn, S., Kim, J., Kim, J.,... & Choi, H. (2006). Drag reduction in flow over a twodimensional bluff body with a blunt trailing edge using a new passive device. Journal of Fluid Mechanics, 563, Naghib-Lahouti, A., Hangan, H., & Lavoie, P. (2015). Distributed forcing flow control in the wake of a blunt trailing edge profiled body using plasma actuators. Physics of Fluids (1994-present), 27(3),

8 Overview of control strategies Type of control Open-loop control Closed-loop control Actuation Steady perturbation Time-dependent perturbation (De)synchronisation shear modification? vortex dislocation Target Primary instability (von Karman v.s.) Secondary instability (streamwise structures)

) can be implemented Linear system identification methods in numerical simulations (low Re numbers) Dahan, J. A., Morgans, A. S., & Lardeau, S. (2012).

9 Model-free vs. model-based control? Natural flow pressure measurements (courtesy of A. Debien, ONERA) Raw signal Filtered signal Phase Model-free feedback control (similar to Stalnov et al.) can be implemented Linear system identification methods in numerical simulations (low Re numbers) Dahan, J. A., Morgans, A. S., & Lardeau, S. (2012). Feedback control for form-drag reduction on a bluff body with a blunt trailing edge. Journal of Fluid Mechanics, 704, Flinois, T., Morgans, A. S. (2016) Feedback control of unstable flows: a direct modelling approach using the Eigensystem Realisation Algorithm. Journal of Fluid Mechanics, 793,

10 Design of the CARPE experiment Digital mock-up (by S. Prothin, ISAE) DBD actuator Pro: high flexibility in position, orientation and controlability Con: proximity of sensors and actuators, EM interference

11 Boundary layer and the global mode frequency y (mm) U (m/s) U 0 (m/s) Re(U 0, D) y (U max )(mm) delta (m) theta (m) Re (theta) H U 0 (m/s) f VKS (Hz) St t (ms)

12 Dielectric Barrier Discharge (DBD) actuator Top-down view of the model Sensors (mounted inside) DBD properties: Electrodes f c = 2.4 khz u peak = 10-20kV i = 24mA U jet 2-4 m/s Strioscopic imagery of the DBD jet propagation in a still environment

13 Control loop design Sensor signal: real time pressure measurements + lowpass filtering P1 g (t) - actuation p 1 p 0 Head pressure sensor p 3 p 2 Pressure sensors on the base P2 Proportional control: g(t+δt) = C s(t) Objective function: C pb = p 3 / p 0

14 Control loop design Sensor signal: real time pressure measurements + lowpass filtering P1 g (t) - actuation p 1 L b p 0 Head pressure sensor p 3 C pb C d p 2 Pressure sensors on the base P2

15 Sensor delay Δt s = 0 Δt s = 3 ms

16 Closed-loop control (I) Δt = 0, ΔΦ (p2) 0 Δt = 25 ms, ΔΦ (p2) = 360 U 0 = 3.5 m/s Re 4900 Actuation (0=ON) (1 - C pb /C pbn )*100 P1 (Pa) ΔΦ (p2) 0 ΔΦ (p1) 0 ΔΦ (p1) = 180 U 0 = 5.1 m/s Re 7000

17 Future tasks Detailed flow study in a large scale setup: - Large scale model easier to integrate with the sensors and the DBD actuator - SABRE wind tunnel facility enables a lower Re number study (similar to numerical simulations) - Time resolved PIV for elucidating on the synchronization mechanism - Close-in PIV to resolve the DBD actuator dynamics vs the boundary/shear layer - Alternative actuator location (at the base, blowing perpendicular to the separated shear layer) - Implementation of a linear model-based controller (partially designed using low Re number simulations from IMT)

18 Thank you!

Drag reduction by closed-loop control of a separated flow over a bluff body with a blunt trailing edge

Proceedings of the 44th IEEE Conference on Decision and Control, and the European Control Conference 25 Seville, Spain, December 12-15, 25 MoA15.1 Drag reduction by closed-loop control of a separated flow