Publications related to Open-loop control of noise amplification in separated boundary layers

Open-loop control of a separated boundary layer

Linear optimal gains

G_{opt}(\omega)

are computed for the separated boundary-layer flow past a two-dimensional bump in the subcritical regime. Very large values are found, making it possible for small-amplitude noise to be strongly amplified and to desta ...

Elsevier France-Editions Scientifiques Medicales Elsevier2014

Sensitivity of stochastic perturbations in a noise amplifier flow

François Gallaire, Edouard Boujo

It is a well-known fact that small-amplitude perturbations can be amplified in globally stable flows due to non-normal mechanisms. This leads in the time domain to the transient growth of some initial disturbances, and in the frequency domain to the amplif ...

2014

A linearized approach for the control of aerodynamic forces in flow past a square cylinder

François Gallaire, Edouard Boujo, Philippe Meliga

The analysis of Strykowski & Sreenivasan (JFM, 1990) provides experimental evidence that a small control cylinder suitably positioned in the wake of a main cylinder can alter vortex shedding close to the instability threshold. This problem was addressed fr ...

2014

An adjoint-based approach to the optimal control of separated flows

Edouard Boujo

Flow separation is relevant to many industrial applications, since it is detrimental to the aerodynamic performance of vehicles, induces vibrations in mechanical structures, but can also contribute to improve mixing in combustion devices. In this thesis, t ...

EPFL2014

Soft Constrained Model Predictive Control With Robust Stability Guarantees

Colin Neil Jones, Melanie Nicole Zeilinger

Soft constrained model predictive control (MPC) is frequently applied in practice in order to ensure feasibility of the optimization during online operation. Standard techniques offer global feasibility by relaxing state or output constraints, but cannot e ...

Institute of Electrical and Electronics Engineers2014

Open-loop control of a separated boundary layer

François Gallaire, Edouard Boujo

Linear optimal gains

G_opt(\omega)

are computed for the separated boundary-layer flow past a two-dimensional bump in the subcritical regime. Very large values are found, making it possible for small-amplitude noise to be strongly amplified and to destabi ...

Cépaduès Editions2013

Forced reattachment in separated flows: a variational approach to recirculation length reduction

François Gallaire, Edouard Boujo

Sensitivity analysis is used to design an open-loop control for separated flows. The length of the recirculation region

l_c

is expressed as a cost functional, and its sensitivity to actuation is derived analytically. This analysis allows to identify regi ...

2013

Stability analysis and control of the flow in a symmetric channel with a sudden expansion

Andrea Fani

The laminar flow in two-dimensional diffusers may produce either symmetric or nonsymmetric steady solutions, depending on the value of the Reynolds number as compared with some critical value. The stability properties of the flow are studied in the context ...

American Institute of Physics2012

Sensitivity of optimal gains in a detached boundary layer

François Gallaire, Edouard Boujo

The flow over a 2D bump at moderate Reynolds numbers is studied as a pro- totype of detached boundary layers. It is well known that such non-normal systems can exhibit large energy amplification even in their stable regime, as characterized by transient gr ...

2012

The influence of shear layer thickness on the stability of confined two-dimensional wakes

François Gallaire, Luca Biancofiore

The influence of confinement onto the inviscid and incompressible linear stability of the family of wakes introduced by Monkewitz [Phys. Fluids 31, 999 (1988)] is examined. The nondimensional parameters of the model, the velocity ratio Λ, defined as ratio ...

2011

Open-loop control of noise amplification in separated boundary layers

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Open-loop control of a separated boundary layer

Sensitivity of stochastic perturbations in a noise amplifier flow

A linearized approach for the control of aerodynamic forces in flow past a square cylinder

An adjoint-based approach to the optimal control of separated flows

Soft Constrained Model Predictive Control With Robust Stability Guarantees

Open-loop control of a separated boundary layer

Forced reattachment in separated flows: a variational approach to recirculation length reduction

Stability analysis and control of the flow in a symmetric channel with a sudden expansion

Sensitivity of optimal gains in a detached boundary layer

The influence of shear layer thickness on the stability of confined two-dimensional wakes

Sensitivity of stochastic perturbations in a noise amplifier flow

Soft Constrained Model Predictive Control With Robust Stability Guarantees

Sensitivity of optimal gains in a detached boundary layer

The influence of shear layer thickness on the stability of confined two-dimensional wakes

Open-loop control of a separated boundary layer

Open-loop control of a separated boundary layer

A linearized approach for the control of aerodynamic forces in flow past a square cylinder

An adjoint-based approach to the optimal control of separated flows

Forced reattachment in separated flows: a variational approach to recirculation length reduction

Stability analysis and control of the flow in a symmetric channel with a sudden expansion