In-flight active wave cancelation with delayed-x-LMS control algorithm in a laminar boundary layer

Simon, Bernhard; Fabbiane, Nicolò; Nemitz, Timotheus; Bagheri, Shervin; Henningson, Dan S.; Grundmann, Sven

doi:10.1007/s00348-016-2242-5

Cited by 15 publications

(6 citation statements)

References 34 publications

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“…With this in mind, in this work we tackle the problem of delaying the transition to turbulence for boundary layers. A long-term objective of such study is the application of the techniques developed herein in flight (as developed, for example, in the work of Simon et al (2016) for a different type of disturbance). Given the intricateness of the subject, we will demonstrate the feasibility of such techniques in the simpler case of a simulated boundary layer developing over a flat plate with a high level of external disturbances, a canonical problem representative of a low subsonic flight, at low altitude, a condition typical of sail planes, for instance.…”

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confidence: 99%

On the role of actuation for the control of streaky structures in boundary layers

et al. 2019

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This work deals with the closed-loop control of streaky structures induced by free-stream turbulence (FST) in a zero-pressure gradient, transitional boundary layer, by means of localized sensors and actuators. A linear quadratic gaussian regulator is considered along with a system identification technique to build reduced-order models for control. Three actuators are developed with different spatial supports, corresponding to a baseline shape with only vertical forcing, and to two other shapes obtained by different optimization procedures. A computationally efficient method is derived to obtain an actuator which aims to induce the exact structures which are inside the boundary layer, given in terms of their first spectral proper orthogonal decomposition (SPOD) mode, and an actuator that maximizes the energy of induced downstream structures. Two free-stream turbulence levels were evaluated, corresponding to 3.0% and 3.5%, and closed-loop control is applied in large-eddy simulations of transitional boundary layers. All three actuators lead to significant delays in the transition to turbulence and were shown to be robust to mild variations in the free-stream turbulence levels. Differences are understood in terms of the SPOD of actuation and FST-induced fields along with the causality of the control scheme when a cancellation of disturbances is considered. The actuator optimized to generate the leading downstream SPOD mode, representing the streaks in the open-loop flow, leads to the highest transition delay, which can be understood due to its capability of closely cancelling structures in the boundary layer. However, it is shown that even with the actuator located downstream of the input measurement it may become impossible to cancel incoming disturbances in a causal way, depending on the wall-normal position of the output and on the actuator considered, which limits sensor and actuator placement capable of good closed-loop performance.

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On the role of actuation for the control of streaky structures in boundary layers

et al. 2019

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“…A similar approach was used by Luhar et al (2014), where opposition control based on the resolvent operator was performed. Adaptive control strategies are often similar to wave-cancellation approaches, but use additional downstream sensors to adapt the control law to changes in the flow (Fabbiane et al 2014;Simon et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Resolvent-based tools for optimal estimation and control via the Wiener–Hopf formalism

et al. 2022

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The application of control tools to complex flows frequently requires approximations, such as reduced-order models and/or simplified forcing assumptions, where these may be considered low rank or defined in terms of simplified statistics (e.g. white noise). In this work we propose a resolvent-based control methodology with causality imposed via a Wiener–Hopf formalism. Linear optimal causal estimation and control laws are obtained directly from full-rank, globally stable systems with arbitrary disturbance statistics, circumventing many drawbacks of alternative methods. We use efficient, matrix-free methods to construct the matrix Wiener–Hopf problem, and we implement a tailored method to solve the problem numerically. The approach naturally handles forcing terms with space–time colour; it allows inexpensive parametric investigation of sensor/actuator placement in scenarios where disturbances/targets are low rank; it is directly applicable to complex flows disturbed by high-rank forcing; it has lower cost in comparison to standard methods; it can be used in scenarios where an adjoint solver is not available; or it can be based exclusively on experimental data. The method is particularly well suited for the control of amplifier flows, for which optimal control approaches are typically robust. Validation of the approach is performed using the linearized Ginzburg–Landau equation. Flow over a backward-facing step perturbed by high-rank forcing is then considered. Sensor and actuator placement are investigated for this case, and we show that while the flow response downstream of the step is dominated by the Kelvin–Helmholtz mechanism, it has a complex, high-rank receptivity to incoming upstream perturbations, requiring multiple sensors for control.

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“…A similar approach was used by [5], where opposition control based on the resolvent operator was performed. Adaptive control strategies are often similar to wave-cancellation approaches, but use additional downstream sensors to adapt the control law to changes in the flow [13,14].…”

Section: Introductionmentioning

confidence: 99%

Resolvent-based tools for optimal estimation and control via the Wiener-Hopf formalism

Martini,

Jung,

Cavalieri

et al. 2022

Preprint

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The application of control tools to complex flows frequently requires approximations, such as reduced-order models and/or simplified forcing assumptions, where these may be considered low-rank or defined in terms of simplified statistics (e.g. white noise). In this work, we propose a resolvent-based control methodology with causality imposed via a Wiener-Hopf formalism. Linear optimal causal estimation and control laws are obtained directly from full-rank, globally stable systems with arbitrary disturbance statistics, circumventing many drawbacks of alternative methods. We use efficient, matrix-free methods to construct the matrix Wiener-Hopf problem, and we implement a tailored method to solve the problem numerically. The approach naturally handles forcing terms with space-time colour; it allows inexpensive parametric investigation of sensor/actuator placement in scenarios where disturbances/targets are low rank; it is directly applicable to complex flows disturbed by high-rank forcing; it has lower cost in comparison to standard methods; it can be used in scenarios where an adjoint solver is not available; or it can be based exclusively on experimental data. The method is particularly well-suited for the control of amplifier flows, for which optimal control approaches are typically robust. Validation of the approach is performed using the linearized Ginzburg-Landau equation. Flow over a backward-facing step perturbed by high-rank forcing is then considered. Sensor and actuator placement are investigated for this case, and we show that while the flow response downstream of the step is dominated by the Kelvin-Helmholtz mechanism, it has a complex, high-rank receptivity to incoming upstream perturbations, requiring multiple sensors for control.

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In-flight active wave cancelation with delayed-x-LMS control algorithm in a laminar boundary layer

Cited by 15 publications

References 34 publications

On the role of actuation for the control of streaky structures in boundary layers

On the role of actuation for the control of streaky structures in boundary layers

Resolvent-based tools for optimal estimation and control via the Wiener–Hopf formalism

Resolvent-based tools for optimal estimation and control via the Wiener-Hopf formalism

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