Transition delay in a boundary layer flow using active control

Semeraro, Onofrio; Bagheri, Shervin; Brandt, Luca; Henningson, Dan S.

doi:10.1017/jfm.2013.299

Cited by 45 publications

(42 citation statements)

References 40 publications

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“…Another approach is the use of system identification methods in which low order models are obtained from a sample of input-output measurements. In particular the eigensystem realisation algorithm (ERA) (Juang & Pappa 1985) was recently used to construct reduced order models for fluid flows (Ma et al 2011;Illingworth et al 2012;Dadfar et al 2013;Semeraro et al 2013;Belson et al 2013;Flinois & Morgans 2016). ERA is based on the impulse response measurements and does not require prior knowledge of the high order system.…”

Section: Model Reduction and Localised Controlmentioning

confidence: 99%

“…For localised transition control the disturbance is commonly represented by a localised body force placed upstream of the control actuators, see e.g. Bagheri et al (2009b); Semeraro et al (2011Semeraro et al ( , 2013; Belson et al (2013). For example, in Semeraro et al (2011) the disturbance was modelled as a localised initial condition that provides the maximum energy amplification of the perturbation at a given final time.…”

Section: Scope and Outline Of The Present Studymentioning

confidence: 99%

“…A feedforward actuator/sensor configuration (Belson et al 2013) is considered in which upstream sensors are used to detect the incoming perturbations. Such a set-up is commonly considered for convectively unstable flows (Bagheri et al 2009b;Semeraro et al 2013; and guarantees the best nominal performance (Belson et al 2013). Nonetheless a feedforward approach can be more sensitive to unmodelled disturbances/dynamics as compared to feedback configurations as argued in (Belson et al 2013).…”

Section: Scope and Outline Of The Present Studymentioning

confidence: 99%

“…The application of linear control theory to fluid flows is therefore considered as a viable route to suppress instabilities and delay transition for reducing skin-friction drag (Joshi et al 1997;Cortelezzi & Speyer 1998;Bewley & Liu 1998;Högberg et al 2003a;Baramov et al 2004;Chevalier et al 2007;Bagheri et al 2009b;Semeraro et al 2013;Jones et al 2015). In particular, optimal multivariable control strategies (LQG/H 2 , H ∞ ) (Zhou et al 1996;Skogestad & Postlethwaite 2005) have been successfully applied, see Kim & Bewley (2007); ; for an in-depth review on this subject.…”

Section: Introductionmentioning

confidence: 99%

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Localised estimation and control of linear instabilities in two-dimensional wall-bounded shear flows

et al. 2017

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A new framework is presented for estimation and control of instabilities in wall-bounded shear flows described by the linearised Navier-Stokes equations. The control design considers the use of localised actuators/sensors to account for convective instabilities in an H 2 optimal control framework. External sources of disturbances are assumed to enter the control domain through the inflow. A new inflow disturbance model is proposed for external excitation of the perturbation modes that contribute to transition. This model allows efficient estimation of the flow perturbations within the localised control region of a conceptually unbounded domain. The state-space discretisation of the infinite dimensional system is explicitly obtained, which allows application of linear control theoretic tools. A reduced order model is subsequently derived using exact balanced truncation that captures the input/output behaviour and the dominant perturbation dynamics. This model is used to design an H 2 optimal controller to suppress the instability growth. The 2-D non-periodic channel flow is considered as an application case. Disturbances are generated upstream of the control domain and the resulting flow perturbations are estimated/controlled using point wall shear measurements and localised unsteady blowing and suction at the wall. The controller is able to cancel the perturbations and is robust to both unmodelled disturbances and sensor inaccuracies. For single frequency and multiple frequency disturbances with low sensor noise nearly a full cancellation is achieved. For stochastic forced disturbances and high sensor noise an energy reduction in perturbation wall shear stress of 96% is shown.

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Section: Model Reduction and Localised Controlmentioning

confidence: 99%

Section: Scope and Outline Of The Present Studymentioning

confidence: 99%

Section: Scope and Outline Of The Present Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Localised estimation and control of linear instabilities in two-dimensional wall-bounded shear flows

et al. 2017

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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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Full-order optimal compensators for flow control: the multiple inputs case

Semeraro

Pralits

2018

Theor. Comput. Fluid Dyn.

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Flow control has been the subject of numerous experimental and theoretical works. In this numerical study, we analyse full-order, optimal controllers for large dynamical systems in presence of multiple actuators and sensors. We start from the original technique proposed by [1], the adjoint of the direct-adjoint (ADA) algorithm. The algorithm is iterative and allows bypassing the solution of the algebraic Riccati equation associated with the optimal control problems, typically unfeasible for large systems.We extend ADA into a more generalized framework that includes the design of multi-input, coupled controllers and robust controllers based on the H ∞ framework. The full-order controllers do not require any preliminary step of model reduction or low-order approximation: this feature allows to preassess the optimal performances of an actuated flow without relying on any estimation process or further hypothesis.We show that the algorithm outperforms analogous technique, in terms of convergence performances considering two numerical cases: a distributed system and the linearized Kuramoto-Sivashinsky equation, mimicking a full three-dimensional control setup. For the ADA algorithm we find excellent scalability with the number of inputs (actuators) in terms of convergence to the solution, making the method a viable way for full-order controller design in complex settings.

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Transition delay in a boundary layer flow using active control

Cited by 45 publications

References 40 publications

Localised estimation and control of linear instabilities in two-dimensional wall-bounded shear flows

Localised estimation and control of linear instabilities in two-dimensional wall-bounded shear flows

On the role of adaptivity for robust laminar flow control

Full-order optimal compensators for flow control: the multiple inputs case

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