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The main contribution of this paper is the derivation of spatiotemporal Liénard-type models for expressing the dynamical behavior of a fluid transmission line. The derivation is carried out from a quasilinear hyperbolic system made of a momentum equation and a continuity one. An advantage of these types of models is that they are suitable for formulating estimation algorithms. This claim is confirmed in the present paper for the case of fluid dynamics, since the article presents the conception and evaluation of a Liénard model-based observer that estimates the parameters of a pipeline such as the friction factor, the equivalent length and the wave speed. To show the potentiality of the approach, results based on some simulation and experimental tests are presented. [ABSTRACT FROM AUTHOR]

Abstract: The damping properties estimation assumes a viscoelastic model calibrated from experiments and simulations. This Note presents a gradient method for viscoelastic behaviour identification of damped sandwich structures devoted to the passive control of mechanical vibration. The method combines experimental data, numerical simulations realized with a complex non-linear eigenvalue solver using the asymptotic numerical method, and optimal control for the identification of viscoelastic parameters. An automatic differentiation tool is used to get numerical derivatives exact up to the machine precision with minimal user effort. Results are presented for a sandwich beam with a frequency dependent viscoelastic core. [Copyright &y& Elsevier]

Abstract: A variational data assimilation method is applied to a simplified marine ecosystem model of NPZ (Nutrient Phytoplankton Zooplankton) type, which implies five parameters. The method allows us to optimise these parameters by an iterative process of minimisation of a cost function which quantifies the quadratic discrepancy between observations and simulation results. The first part of this note describes how to obtain the adjoint model of the NPZ model allowing us to compute the gradient of the cost function relative to the parameters. Two experiments of artificial data assimilation then show the efficiency of this method, but also its limitations because of non-linearities and sensitivity problems of the model relative to the parameters. To cite this article: Y. Leredde et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

Un mate´riau destine´ a` subir de fortes contraintes thermome´caniques peut eˆtre prote´ge´ d'une usure pre´coce par un reveˆtement de´pose´ par voie e´lectrolytique. Nous nous proposons dans cet article de caracte´riser ce type de reveˆtement par une me´thode de controˆle non-destructif : la me´thode flash en face avant. Apre`s re´solution d'un proble`me inverse de transferts thermiques, nous obtenons les valeurs des diffusivite´s et des effusivite´s du de´poˆt, qui serviront a` estimer l'efficacite´ de sa protection. Ces valeurs seront aussi utilise´es comme donne´es d'entre´es de codes de calculs thermome´caniques. Les parame`tres sont identifie´s par une me´thode ite´rative de minimisation des e´carts quadratiques entre les mesures et les valeurs calcule´es par un mode`le, la me´thode de Box–Kanemasu modifie´e par Bard. Plusieurs mode`les sont de´veloppe´s et compare´s afin d'estimer leurs performances. Cette comparaison permet de mettre en œuvre une proce´dure de re´gularisation du proble`me inverse par re´duction du nombre de parame`tres. Une e´tude de sensibilite´ exhaustive permet de concevoir de fac¸on optimale le mode ope´ratoire expe´rimental. Une estimation de la re´sistance thermique de contact entre le de´poˆt et son substrat mene´e a` partir de mesures obtenues sur deux e´chantillons diffe´rents de chrome e´lectrolytique sur substrat d'acier permettent de mettre en e´vidence une e´volution des proprie´te´s de la couche protectrice et de la qualite´ de l'interface. [Copyright 2004 Elsevier]

We propose a one-equation model for two-dimensional turbulent flow through porous media. The momentum equation is derived from the space averaging of Navier–Stokes equations, leading to the so-called Darcy–Forchheimer equations. In the turbulent kinetic energy transport equation, the production term is assumed to be proportional to the cube of velocity. The dissipation term is not estimated with a transport equation, it is explicitly given by a law involving turbulent kinetic energy and velocity. The model requires only four experimentally determined parameters. The local Nusselt number was correlated to local Reynolds number, and to local turbulence intensity. Good agreement between the simulated and the experimental local Nusselt number is obtained. [Copyright &y& Elsevier]