Laminar flow control with distributed surface actuation: damping Tollmien-Schlichting waves with active surface displacement

Goldin, Nikolas; King, Rudibert; Pätzold, Andreas; Nitsche, W.; Haller, Daniel; Woias, Peter

doi:10.1007/s00348-013-1478-6

Cited by 11 publications

(14 citation statements)

References 19 publications

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“…This definition underlines the dependency of the control input u(t) from the measurements y(t). By considering the relation in frequency domain and inserting it into the plant (27), the closed-loop system between d(s) and z(s) is obtained in the form, z(s) = P zd (s) + P zu (s) K uy (s) P yd (s)…”

Section: Closed-loop Systemmentioning

confidence: 99%

“…This can be accomplished using the second sensor z -downstream of the actuator -in combination with the estimation sensor y -placed upstream of the actuator. The combination of feedback and feedforward is the underlying idea of the MPC controller applied to our configuration [27]. However, there are some drawbacks due to the computational costs of the algorithm; indeed, the entries of the dynamic matrix (51) are computed during the prediction-step using time integration, whose domain increases with the time-delays of the system.…”

Section: Model Uncertaintiesmentioning

confidence: 99%

“…Whereas both numerical and experimental approaches have pushed forward flow control research, they have in a large extent evolved disconnected from each other; the systems control theoretical approach has provided very important insights into physical mechanisms and constraints that has to be addressed in order to design active control that is optimal and robust, but most work has stayed at a proofof-concept level and have not yet been fully implemented in practical applications. Although, there are exceptions [26,27], the majority of experimental active control has essentially suffered from the opposite; most controllers are developed directly in the experimental setting on a trial-anderror basis, with many tuning parameters, that have to be chosen for each particular set-up.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Adaptive and Model-Based Control Theory Applied to Convectively Unstable Flows

Fabbiane

Semeraro

Bagheri

et al. 2014

Applied Mechanics Reviews

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Adaptive and model-based control theory applied to convectively unstable flows. Review, 66(6) Research on active control for the delay of laminar-turbulent transition in boundary layers has made a significant progress in the last two decades, but the employed strategies have been many and dispersed. Using one framework, we review model-based techniques, such as linear-quadratic regulators, and model-free adaptive methods, such as least-mean square filters. The former are supported by a elegant and powerful theoretical basis, whereas the latter may provide a more practical approach in the presence of complex disturbance environments, that are difficult to model. We compare the methods with a particular focus on efficiency, practicability and robustness to uncertainties. Each step is exemplified on the one-dimensional linearized Kuramoto-Sivashinsky equation, that shows many similarities with the initial linear stages of the transition process of the flow over a flat plate. Also, the source code for the examples are provided. Applied Mechanics

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Section: Closed-loop Systemmentioning

confidence: 99%

Section: Model Uncertaintiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Adaptive and Model-Based Control Theory Applied to Convectively Unstable Flows

Fabbiane

Semeraro

Bagheri

et al. 2014

Applied Mechanics Reviews

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“…In a low-turbulence environment the initial phase of the transition process is an exponential growth of Tollmien-Schlichting (TS) waves (Saric, Reed & Kerschen 2002). Both numerical and laboratory experiments have shown that it is possible to use linear control techniques to damp the amplitude of the instabilities by several orders of magnitude, with the consequences that the transition is delayed and the skin-friction drag is reduced (Lundell 2007;Bagheri & Henningson 2011;Goldin et al 2013;Semeraro et al 2013a). However, the linear control approach has not yet been established as a competitive technique in applied settings, and essentially all work is at a proof-of-concept level.…”

Section: Introductionmentioning

confidence: 99%

On the role of adaptivity for robust laminar flow control

et al. 2015

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In boundary-layer flows, one may reduce skin-friction drag by delaying the onset of laminar-to-turbulent transition via the attenuation of small-amplitude Tollmien-Schlichting (TS) waves. In this work, we use numerical simulations and experiments to compare the robustness of adaptive and model-based techniques for reducing the growth of two-dimensional TS disturbances. In numerical simulations, the optimal linear quadratic Gaussian (LQG) regulator shows the best performance under the conditions it was designed for. However, it is found that the performance deteriorates linearly with the drift of the Reynolds number from its nominal value. As a result, an order-of-magnitude loss of performance is observed when applying the computation-based LQG controller in wind-tunnel experiments. In contrast, it is shown that the adaptive filtered-X least-mean-squares (FXLMS) algorithm is able to maintain an essentially constant performance for significant deviations of the nominal values of the disturbance amplitude and Reynolds number.

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“…Goldin et al 2013;Fabbiane et al 2014;Ghiglieri & Ulbrich 2014). This approach can also be used as an off-line adjoint-based optimisation technique if applied to the full (potentially nonlinear) Navier-Stokes equations (e.g.…”

mentioning

confidence: 99%

Feedback control of unstable flows: a direct modelling approach using the Eigensystem Realisation Algorithm

Flinois

Morgans

2016

J. Fluid Mech.

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Obtaining low-order models for unstable flows in a systematic and computationally tractable manner has been a long-standing challenge. In this study, we show that the Eigensystem Realisation Algorithm (ERA) can be applied directly to unstable flows, and that the resulting models can be used to design robust stabilising feedback controllers. We consider the unstable flow around a D-shaped body, equipped with body-mounted actuators, and sensors located either in the wake or on the base of the body. A linear model is first obtained using approximate balanced truncation. It is then shown that it is straightforward and justified to obtain models for unstable flows by directly applying the ERA to the open-loop impulse response. We show that such models can also be obtained from the response of the nonlinear flow to a small impulse. Using robust control tools, the models are used to design and implement both proportional and H ∞ loop-shaping controllers. The designed controllers were found to be robust enough to stabilise the wake, even from the nonlinear vortex shedding state and in some cases at off-design Reynolds numbers.

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Laminar flow control with distributed surface actuation: damping Tollmien-Schlichting waves with active surface displacement

Cited by 11 publications

References 19 publications

Adaptive and Model-Based Control Theory Applied to Convectively Unstable Flows

Adaptive and Model-Based Control Theory Applied to Convectively Unstable Flows

On the role of adaptivity for robust laminar flow control

Feedback control of unstable flows: a direct modelling approach using the Eigensystem Realisation Algorithm

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