Fabien Wahl

Laboratoire Jacques-Louis Lions

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Yoshinobu TSUJIMOTO

Osaka University

Hironori HORIGUCHI

Osaka University

Martin Parisot

Institut national de recherche en informatique et en automatique

Jacques Sainte-Marie

Institut national de recherche en informatique et en automatique

Edwige Godlewski

Laboratoire Jacques-Louis Lions

Dai Kataoka

Honda (Japan)

Satoshi Watanabe

Kyushu University

Yoshiki YOSHIDA

Japan Aerospace Exploration Agency

Satoshi Watanabe

Kyoto University

H Meubrink

Cooperative Institutions

Kyushu University

The University of Tokyo

Osaka University

Osaka Health Science University

Institut national de recherche en informatique et en automatique

Laboratoire Jacques-Louis Lions

Centre National de la Recherche Scientifique

Sorbonne Université

Université Paris Cité

Centre d'Études et d'Expertise sur les Risques, l'Environnement, la Mobilité et l'Aménagement

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Modeling and analysis of interactions between free surface flows and floating structures

HAL (Le Centre pour la Communication Scientifique Directe) (2018)

Fabien Wahl

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Modélisation et analyse des interactions entre écoulements à surface libre et objets flottants

Fabien Wahl

Cette these traite de la modelisation et de la resolution numerique d'ecoulements en presence d'une structure a la surface. On considere la problematique d'un objet flottant sur un grand domaine. Les ecoulements sous la banquise et la production d'energie renouvelable grâce a des bouees sont des applications potentielles de ce travail. Nous derivons un modele de type Saint-Venant avec une contrainte de congestion supplementaire. La contrainte de congestion est un defi pour la resolution numerique d'equations hyperboliques. Nous proposons alors un modele unifie base sur une relaxation pseudo-compressible pour la resolution. Nous identifions les proprietes necessaires a la resolution numerique et decrivons l'adaptation d'un schema volumes finis. La preservation de l'etat d'equilibre du lac au repos ainsi qu'une loi de dissipation pour l'energie mecanique sont demontrees sous une condition non-restrictive sur le pas de temps. Pour prendre en compte un objet flottant librement, nous introduisons un couplage entre le modele de Saint-Venant congestionne et les equations du mouvement donnees par le principe fondamental de la dynamique en nous concentrant sur l'energie du systeme couple. Cet aspect est en effet d'un interet majeur dans la production d'energie. Un schema de Newmark est utilise pour le solide et couple a la resolution numerique pour le fluide. Nous proposons une correction entropique basee sur un choix de discretisation particulier des termes de couplage pour assurer une loi de dissipation au niveau discret. La methode est validee en dimension un sur des solutions analytiques stationnaires et non-stationnaires.

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Sur les effets non-hydrostatiques en eaux profondes : application à la simulation de tsunamis

HAL (Le Centre pour la Communication Scientifique Directe) (2015)

Fabien Wahl

Dans ce travail, on s’interesse a la modelisation de la propagation d’une vague et plus precisement, on aimerait savoir ce qui se passe quand l’hypothese d'eaux peu profondes n’est plus verifiee. Souvent des modeles hydrostatiques sont utilises dans lesquels la pression en un point est definie comme l’acceleration de la pesanteur multiplie par la hauteur d’eau au dessus de ce point. Ces modeles simplifies negligent la partie non-hydrostatique de la pression, definie comme la difference entre la pression hydrostatique et la pression reelle. On compare un modele non-hydrostatique a un modele classique de type Saint-Venant. En eaux profondes, des effets non-hydrostatiques apparaissent et on cherche a en decrire l’impact sur l’amplitude et la forme des vagues. Nous presenterons la derivation du modele a partir des equations de Navier-Stokes puis nous identifierons une solution analytique. Enfin, nous presenterons des resultats numeriques afin de comparer le modele au modele de Saint-Venant.

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Congested shallow water type model: roof modelling in free surface flow

HAL (Le Centre pour la Communication Scientifique Directe) (2016)

Edwige Godlewski Martin Parisot Jacques Sainte-Marie Fabien Wahl

We are interested in the modeling and the numerical approximation of flows in the presence of a roof, for example flows in sewers or under an ice floe. A shallow water model with a supplementary congestion constraint describing the roof is derived from the Navier-Stokes equations. The congestion constraint is a challenging problem for the numerical resolution of hyperbolic equations. To overcome this difficulty, we follow a pseudo-compressibility relaxation approach. Eventually, a numerical scheme based on a Finite Volume method is proposed. The well-balanced property and the dissipation of the mechanical energy, acting as a mathematical entropy, are ensured under a non-restrictive condition on the time step in spite of the large celerity of the potential waves in the congested areas. Simulations in one dimension for transcritical steady flow are carried out and numerical solutions are compared to several analytical (stationary and non-stationary) solutions for validation.

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[Chronic benzene poisoning in roof tilers].

PubMed (1969)

N Kliche H Meubrink Fabien Wahl

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Congested shallow water model: floating object

HAL (Le Centre pour la Communication Scientifique Directe) (2018)

Edwige Godlewski Martin Parisot Jacques Sainte-Marie Fabien Wahl

We are interested in the floating body problem on a large space scale. We focus on objects floating freely in the water such as icebergs or wave energy converters. The formulation of the fluid-solid interaction using the congested shallow water model for the fluid and Newton's second law of motion for the solid is given and a strong coupling between the two systems is explained. The energy transfer between the solid and the water is focused on since it is of major interest for energy production. A numerical resolution based on the coupling of a finite volume scheme for the fluid and a Newmark scheme for the solid is presented. An entropy correction based on an adapted choice of discretization for the coupling terms is made in order to ensure a dissipation law at the discrete level. Simulations are presented to validate the method and to show the feasibility of more complex cases.

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Steady Flow and Stability Analyses of Cavitation in Finite Blade Count Impeller

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B (1999)

Hironori HORIGUCHI Fabien Wahl Satoshi Watanabe Yoshinobu TSUJIMOTO

The seady flow and stability analyses of cavitation in fiat plate cascades corresponding to 2, 3, 4 and 5 bladed impeller were carried out to find out all of the steady cavity patterns and destabilizing modes. For this purpose each blade is treated independently. In steady flow analysis the alternate blade cavitation was found only for impellers with even number of blades. It was shown that the alternate blade cavitation occurs since the local flow near the cavity closure reduces the angle of attack to the opposing blade when the cavity closure point approaches the leading edge of the opposing blade. For 2 or 4 bladed impeller, it was confirmed that there exists no additional destabilizing mode to those found in an analysis assuming inter-blade phase difference. It was shown that the modes with total cavity volume fluctuation depend on the inlet duct length while the modes without total cavity volume fluctuation are independent on the system.

Leading edge

10.1299/kikaib.65.2672

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Effects of Alternate Leading Edge Cutback on Unsteady Cavitation in 4-Bladed Inducers

Journal of Fluids Engineering (2001)

Yoshiki YOSHIDA Yoshinobu TSUJIMOTO Dai Kataoka Hironori HORIGUCHI Fabien Wahl

A set of 4-bladed inducers with various amounts of cutback was tested with the aim of suppressing the rotating cavitation by applying alternate leading edge cutback. Unsteady cavitation patterns were observed by means of inlet pressure measurements and high-speed video pictures. It was found that the region with the alternate blade cavitation and asymmetric cavitation were enlarged with the increase of the amount of the cutback. As a result, the region with the rotating cavitation was diminished. At low flow rate, two types of alternate blade cavitation were found as predicted theoretically on 4-bladed inducer with smaller uneven blade length. One of them is with longer cavities on longer blades, and the other is with longer cavities on shorter blades. Switch was observed in these alternate blade cavitation patterns depending whether the cavitation number was increased or decreased. For an inducer with larger amount of cutback, the rotating cavitation and cavitation surge were almost suppressed as expected for a wide range of flow rate and cavitation number, although the cavitation performance was deteriorated. However, we should note that an asymmetric cavitation pattern occurs more easily in inducers with alternate leading edge cutback, and that the unevenness due to the cutback causes uneven blade stress.

Inducer

Leading edge

10.1115/1.1411969

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Citations (41)

Congested shallow water model: roof modelling in free surface flow

HAL (Le Centre pour la Communication Scientifique Directe) (2018)

Edwige Godlewski Martin Parisot Jacques Sainte-Marie Fabien Wahl

Free surface

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Theoretical Analysis of Cavitation in Inducers with Uneven Length Blades : (2nd Report, Effects of the Amount of Cutting Back)

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B (1999)

Hironori HORIGUCHI Fabien Wahl Satoshi Watanabe Yoshinobu TSUJIMOTO

The present report describes about the effects of the amount of the alternate cutting back of the leading edges on the steady cavitation, its stability and the onset region of rotating cavitation. It was found that, by increasing the amount of cutting back, we can increase the range of cavitation number with stable cavitation and diminish the onset region of rotating cavitation.

Cavitation Erosion

10.1299/kikaib.65.1249

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