Michel Bergmann

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In this paper, optimal control theory is used to minimize the total mean drag for a circular cylinder wake flow in the laminar regime (Re = 200). The control parameters are the amplitude and the frequency of the time-harmonic cylinder rotation. In order to reduce the size of the discretized optimality system, a Proper Orthogonal Decomposition (POD)(More)
This paper focuses on improving the stability as well as the approximation properties of Reduced Order Models (ROM) based on Proper Orthogonal Decomposition (POD). The ROM is obtained by seeking a solution belonging to the POD sub-space and that at the same time minimizes the Navier-Stokes residuals. We propose a modified ROM that directly incorporates the(More)
In this report we investigate the optimal control approach for the active control of the laminar circular cylinder wake flow (Re = 200). The objective is the minimization of the mean total drag where the control function is the time harmonic angular velocity of the rotating cylinder. When the Navier-Stokes equations are used as state equations, the(More)
In this paper we investigate the optimal control approach for the active control of the circular cylinder wake flow considered in the laminar regime (Re = 200). The objective is the minimization of the mean total drag where the control function is the time harmonic angular velocity of the rotating cylinder. When the Navier-Stokes equations are used as state(More)
A computational model is used to examine the effect of caudal fin flexibility on the propulsive efficiency of a self-propelled swimmer. The computational model couples a penalization method based Navier-Stokes solver with a simple model of flow induced deformation and self-propelled motion at an intermediate Reynolds number of about 1000. The results(More)
We propose an optimal sampling strategy to build a robust low-order model. This idea is applied to the construction of a vortex wake model accurate for several regimes. In addition we explore the relationships between unstable modes and low-order modelling. An example of control based on a linearized approach is presented. Résumé : Nous proposons une(More)
This report focuses on improving the stability as well as the approximation properties of Reduced Order Models (ROM) based on Proper Orthogonal Decomposition (POD). The ROM is obtained by seeking a solution belonging to the POD subspace and that at the same time minimizes the Navier-Stokes residuals. We propose a modified ROM that directly incorporates the(More)
Dans cette communication nous nous intéressons à la simulation numérique de la nage de poissons dans un fluide réel. Mathématiquement, l’écoulement est gouverné par les équations de Navier Stokes incompressibles. Numériquement ces équations sont discrétisées en espace sur une grille cartésienne par différences finies centrées d’ordre deux pour les termes(More)