Louvain-la-Neuve, Belgium
Louvain-la-Neuve, Belgium

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Charnomordic B.,Montpellier SupAgro | David R.,CESAME | Dochain D.,CESAME | Hilgert N.,Montpellier SupAgro | And 3 more authors.
Mathematical and Computer Modelling of Dynamical Systems | Year: 2010

In this article, two modelling approaches are proposed for winemaking fermentations. The first one is largely based on the first principle modelling approach and considers the main yeast physiological mechanisms. The model accurately predicts the fermentation kinetics of more than 80% of a large number of experiments performed with 20 wine yeast strains, 69 musts and different fermentation conditions. Thanks to the wide domain of validity of the model, a simulator based on this model coupled to a thermal model was developed to help winemakers to optimize tank management. It predicts the end of the fermentation and changes in the rate of fermentation but furthermore includes an optimization module based on fuzzy logic which allows, via temperature profiles and nitrogen addition strategies, to decrease the duration of fermentation and the energy requirements at winery scale according to user specifications. The objective of the second modelling approach is the development of a mathematical model of the fermentation process including some minority by-products known as characteristic flavour compounds. It refers to metabolic engineering and accounts for the intracellular behaviour of the yeast Saccharomyces cerevisiae by using approaches like the metabolic flux analysis (MFA) and the elementary flux modes (EFMs). A state of the art describes the application of these methods in the restrained field of winemaking/ fermentation conditions and underlines the potential of such approaches. © 2010 Taylor & Francis.

David R.,CESAME | Dochain D.,CESAME | Mouret J.-R.,Montpellier SupAgro | Vande Wouwer A.,University of Mons | Sablayrolles J.-M.,Montpellier SupAgro
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2011

The aromatic profile of a wine is mainly determined during the grape-must fermentation and is characterized by several compounds called flavour markers. These particular compounds are minority by-products produced from "leaks of metabolism" of the used yeast. The final objective of this work is to gain more insight about the synthesis of the aromatic profile in order to optimize it. For this purpose, a first necessary step is the development of a model representing the main physiological phenomena observed during the batch fermentation in the wine-making process in order to later extend it with flavour-markers equations. The main-kinetics model described in this paper is based on a set of biological reactions in which nitrogen compounds such as hexose transporters play a central role, in line with experimental evidence deduced from extensive experimental studies (Malherbe, 2003). © 2011 IFAC.

Melchior S.A.,CESAME | Legat V.,CESAME | van Dooren P.,CESAME | Wathen A.J.,Computing Laboratory
International Journal for Numerical Methods in Fluids | Year: 2012

Solving efficiently the incompressible Navier-Stokes equations is a major challenge, especially in the three-dimensional case. The approach investigated by Elman et al. (Finite Elements and Fast Iterative Solvers. Oxford University Press: Oxford, 2005) consists in applying a preconditioned GMRES method to the linearized problem at each iteration of a nonlinear scheme. The preconditioner is built as an approximation of an ideal block-preconditioner that guarantees convergence in 2 or 3 iterations. In this paper, we investigate the numerical behavior for the three-dimensional lid-driven cavity problem with wedge elements; the ultimate motivation of this analysis is indeed the development of a preconditioned Krylov solver for stratified oceanic flows which can be efficiently tackled using such meshes. Numerical results for steady-state solutions of both the Stokes and the Navier-Stokes problems are presented. Theoretical bounds on the spectrum and the rate of convergence appear to be in agreement with the numerical experiments. Sensitivity analysis on different aspects of the structure of the preconditioner and the block decomposition strategies are also discussed. © 2011 John Wiley & Sons, Ltd.

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