Fluid-Structure Interaction

apport de recherch

Parametric optimization of pulsating jets in unsteady flow by Multiple-Gradient Descent Algorithm (MGDA)

International audienceTwo numerical methodologies are combined to optimize six design characteristics of a system of pulsating jets acting on a laminar boundary layer governed by the compressible Navier-Stokes equations in a time-periodic regime. The flow is simulated by second-order in time and space finite-volumes, and the simulation provides the drag as a function of time. Simultaneously, the sensitivity equations, obtained by differentiating the governing equations w.r.t. the six parametersare also marched in time, and this provides the six-component parametric gradient of drag. When the periodic regime is reached numerically, one thus disposes of an objective-function, drag, to be minimized, and its parametric gradient, at all times of a period. Second, the parametric optimization is conducted as a multi-point problem by the Multiple-Gradient Descent Algorithm (MGDA) which permits to reduce the objective-function at all times simultaneously, and not simply in the sense of a weighted average

Multi-rate data fusion for state and parameter estimation in (Bio-)chemical process engineering

For efficient operation, modern control approaches for biochemical process engineering require information on the states of the process such as temperature, humidity or chemical composition. Those measurement are gathered from a set of sensors which differ with respect to sampling rates and measurement quality. Furthermore, for biochemical processes in particular, analysis of physical samples is necessary, e.g., to infer cellular composition resulting in delayed information. As an alternative for the use of this delayed measurement for control, so-called soft-sensor approaches can be used to fuse delayed multirate measurements with the help of a mathematical process model and provide information on the current state of the process. In this manuscript we present a complete methodology based on cascaded unscented Kalman filters for state estimation from delayed and multi-rate measurements. The approach is demonstrated for two examples, an exothermic chemical reactor and a recently developed model for biopolymer production. The results indicate that the the current state of the systems can be accurately reconstructed and therefore represent a promising tool for further application in advanced model-based control not only of the considered processes but also of related processes

About the Vibration Modes of Square Plate-like Structures

In the experimental vibration analysis of an oil pan, two eigenmodes are observed that did not appear to be those of a standard rectangular plate vibration. As a result, a numerical, analytical and experimental investigation is launched to discover where these modes are originating from. In this paper, the finite element method is applied to determine the vibration behavior numerically, and experimental results are obtained with the help of a laser doppler vibrometer in order to determine the origin of these two eigenmodes

Fast, inexpensive, and reliable HPLC method to determine monomer fractions in poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The determination of the monomer fractions in polyhydroxyalkanoates is of great importance for research on microbial-produced plastic material. The development of new process designs, the validation of mathematical models, and intelligent control strategies for production depend enormously on the correctness of the analyzed monomer fractions. Most of the available detection methods focus on the determination of the monomer fractions of the homopolymer poly(3-hydroxybutyrate). Only a few can analyze the monomer content in copolymers such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate), which usually require expensive measuring devices, a high preparation time or the use of environmentally harmful halogenated solvents such as chloroform or dichloromethane. This work presents a fast, simple, and inexpensive method for the analysis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with high-performance liquid chromatography. Samples from a bioreactor experiment for the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Cupriavidus necator H16 were examined regarding their monomer content using the new method and gas chromatography analysis, one of the most frequently used methods in literature. The results from our new method were validated using gas chromatography measurements and show excellent agreement. Key points ∙ The presented HPLC method is an inexpensive, fast and environmentally friendly alternative to existing methods for quantification of monomeric composition of PHBV. ∙ Validation with state of the art GC measurement exhibits excellent agreement over a broad range of PHBV monomer fractions

Jeux dynamiques en optimisation couplée fluide-structure

International audienceMultidisciplinary optimisation (MDO) adresses the design process of materials and structures that must comply with several criteria, sometimes antagonistic. Moreover, different criteria may be derived from different models, coupled or not. Due to the competing nature of the criteria, rational non-arbitrary methods should be used to drive the MDO, and clearly game theory paradigm offers such a framework. In this paper, we present a case study of MDO in aeronautics, where aerodynamics designer interacts with structural designer in a Nash and Stackelberg games. The developped algorithms as well as numerical results of optimization are presented.L'optimisation multidisciplinaire (MDO) adresse le processus de conception des matériaux et des structures qui doivent être conformes à plusieurs critères, parfois antagonique. D'ailleurs, dif-férents critères qui peuvent résulter de différents modèles, couplés ou pas. En raison de la nature de la concurrence des critères, des méthodes raisonnables non-arbitraires devraient être employées pour conduire le MDO, et clairement le paradigme de la théorie des jeux offre un tel cadre. Dans ce papier, nous présentons un cas d'étude de MDO en aéronautique, où le concepteur aérodynamique intéragit avec le concepteur structural dans le cas du jeu de Nash et de Stackelberg. Les algorithmes développés ainsi que les résultats numériques de l'optimisation seront présentés