Antoine Archer

Bio: Antoine Archer is an academic researcher. The author has contributed to research in topics: Cavitation & Computational fluid dynamics. The author has an hindex of 3, co-authored 5 publications receiving 24 citations.

Numerical Cavitation Intensity on a Hydrofoil for 3D Homogeneous Unsteady Viscous Flows

Abstract: The cavitation erosion remains an industrial issue for many applications. This paper deals with the cavitation intensity, which can be described as the fluid mechanical loading leading to cavitation damage. The estimation of this quantity is a challenging problem both in terms of modeling the cavitating flow and predicting the erosion due to cavitation. For this purpose, a numerical methodology was proposed to estimate cavitation intensity from 3D unsteady cavitating flow simulations. CFD calculations were carried out using Code_Saturne, which enables U-RANS equations resolution for a homogeneous fluid mixture using the Merkle"s model, coupled to a - turbulence model with the Reboud"s correction. A post-process cavitation intensity prediction model was developed based on pressure and void fraction derivatives. This model is applied on a flow around a hydrofoil using different physical (inlet velocities) and numerical (meshes and time steps) parameters. The article presents the cavitation intensity model as well as the comparison of this model with experimental results. The numerical predictions of cavitation damage are in good agreement with experimental results obtained by pitting test.

Etude de la cavitation dans la pompe SHF

Abstract: In order to establish criteria for acceptable erosion, cavitation pitting tests have been performed on several pumps using soft material polished inserts. We present here the results obtained for the SHF centrifugal pump for a range of flowrate from 0.3 to 1.3 Qn. The extent of the pitted zone is recorded and related to the cavity visualization. The pitting is measured using a laser profilometer and quantified by the pitting velocity value, which compares cavitation intensity of each operating condition of the pump. The visualizations are also compared to numerical predictions with CFX.-TASC flow: the cavity sheet development is well predicted by the calcutations.

Compte-rendu des Journées 'Machines hydrauliques, Cavitation' 2017. ENSAM, Campus de Paris 8 et 9 Novembre 2017

Abstract: Les journées ‘Machines hydrauliques et cavitation’ se sont tenues les 8 et 9 Novembre 2017 dans les locaux du Campus ENSAM de Paris. Cette manifestation a été organisée avec le soutien de la SHF, de l’AFM et de l’ENSAM. Elle a réuni 39 participants de 8 nationalités différentes. La majorité des présentations ont été données en anglais. La répartition était relativement équilibrée entre monde académique (17 participants) et industriel (22 participants : fabricants de machines hydrauliques, installateurs, motoristes, exploitants de réseaux hydrauliques et de barrages, bureaux d’études, centres techniques ou de recherche). La fourniture d’un résumé et/ou une inscription par mél étaient seules requises pour la participation à ces journées. Ces journées ont été parfaitement organisées et prises en charge par le Campus ENSAM de Paris, avec le soutien de la Société Hydrotechnique de France. En fin de conférence, un encouragement à publier dans la Houille Blanche a été exprimé. Enfin, une visite des installations d’essais du Laboratoire DynFluid dans les locaux de l’ENSAM (machines hydrauliques et aérauliques) a été organisée en clôture des journées. Au total, 25 présentations ont été proposées lors de ces deux journées, réparties en 7 sessions successives. Le thème général portait sur les machines hydrauliques et la cavitation et les présentations ont porté aussi bien : — sur des retours d’expériences industriels à l’échelle de la machine ou du système — que sur des travaux plus amont portant sur la modélisation ou la compréhension des mécanismes physiques associés aux écoulements internes aux machines hydrauliques et/ ou à la cavitation. Plus précisément, sur la cavitation, les présentations ont particulièrement mis l’accent sur : — La compréhension, par des approches expérimentales, des mécanismes physiques mis en jeu à petite échelle [1], à bas nombre de Reynolds [2] ou dans les tourbillons marginaux [3]. — Des travaux de modélisation numérique de ce type d’écoulement à l’échelle d’une maquette de type foil [4] jusqu’à des machines industrielles [5-7]. — L’érosion de cavitation, du point de vue de son impact sur des turbines Kaplan [8], de sa métrologie [9] ou de l’étude des matériaux les plus performants pour retarder ses effets négatifs [10] — Le dessin et de la performance des inducteurs [11-12]. — La détection de l’apparition de la cavitation ou du collapse par des méthodes acoustiques [13-14]. Dans le domaine des machines hydrauliques ou aérauliques, les travaux présentés lors de ces journées ont porté sur de l’analyse de la physique, à l’échelle du composant [15], ou de la machine lorsqu’elle présente des régimes de fonctionnement instable [16], mais aussi sur de la modélisation fonctionnelle des pompes [17] ou sur des dessins originaux pour des applications particulières dans le domaine de l’industrie pétrolière [18] ou de la production d’énergie [19]. On peut également noter les travaux portant sur la modélisation système, par de la modélisation CFD [20-21] ou par des approches monodimensionnelles pour la prise en compte de certains effets transitoires [22] ou de la dynamique des structures de cavitation [23]. Enfin, citons finalement, deux retours d’expérience rapportant plusieurs décennies de travaux sur, d’une part, l’utilisation de codes de calculs industriels pour le dimensionnement et l’optimisation d’installations hydro-électriques [24] et d’autre part sur le design et l’exploitation de boucles expérimentales pour l’étude de la cavitation [25]. L’ensemble des présentations a ainsi offert un aperçu riche et très varié des travaux en cours dans le domaine des turbomachines hydrauliques. Deux points marquants qui ressortent de ces journées peuvent être notés : • le premier concerne l’utilisation de plus en plus courante de modèles numériques de simulation d’écoulements à

Influence de l'érosion des aubes de la pompe centrifuge " SHF " sur ses caractéristiques hydrauliques : détermination expérimentale sur la boucle EPOCA

Abstract: Afin de determiner l'effet de l'erosion des aubes d'une pompe centrifuge standard (la pompe dite " SHF ") sur ses caracteristiques hydrauliques, des essais sont menes sur la boucle EPOCA a Chatou. L'erosion des aubes, identique pour chacune des aubes et realisee par usinage numerique, est censee representer une usure par erosion de cavitation. Les performances hydrauliques sans cavitation (courbes hauteur, puissance sur l'arbre et rendement en fonction du debit) et le comportement en cavitation (courbe de NPSH3 % et developpements de cavitation a l'entree de la roue) sont mesures pour la roue neuve puis pour trois degres croissants d'usure de la roue : usure legere, usure profonde et usure profonde avec entaille du bord d'attaque. L'evolution des performances est significative, compte tenu des incertitudes de mesure. Pour la geometrie de la pompe SHF, la hauteur avec une roue erodee par rapport a une roue neuve baisse d'environ 2 %, la puissance sur l'arbre baisse au maximum d'environ 9 %. Le NPSH3 % est moderement impacte par l'usure.

Experimental and Numerical Studies in a Centrifugal Pump With Two-Dimensional Curved Blades in Cavitating Condition

Abstract: In the presented study a special test pump with two-dimensional curvature blade geometry was investigated in cavitating and noncavitating conditions using different experimental techniques and a three-dimensional numerical model implemented to study cavitating flows. Experimental and numerical results concerning pump characteristics and performance breakdown were compared at different flow conditions. Appearing types of cavitation and the spatial distribution of vapor structures within the impeller were also analyzed. These results show the ability of the model to simulate the complex three-dimensional development of cavitation in a rotating machinery, and the associated effects on the performance.

Numerical Simulation of 3D Cavitating Flows: Analysis of Cavitation Head Drop in Turbomachinery

Abstract: The numerical simulation of cavitating flows in turbomachinery is studied at the Turbomachinery and Cavitation team of LEGI (Grenoble - France) in collaboration with the French space agency (CNES) and the rocket engine division of SNECMA Moteurs. A barotropic state law is proposed to model the cavitation phenomenon and this model has been integrated in the commercial CFD code Fine/TurboTM, developed and commercialized by Numeca International. The numerical aspects of the work are mainly focused on numerical stability and reliability of the algorithm, when introducing large density variations through the strongly non linear barotropic state law. This research conducted first to changes in the way preconditioning parameters are calculated. Internal flows in turbomachinery have been deeply investigated. A methodology allowing the numerical simulation of the head drop induced by the development of cavitation has been proposed on the basis of computations in inducers and centrifugal pumps. These simulations have allowed the characterization of the mechanisms leading to the head drop and the visualization of the effects of the development of cavitation on internal flows.

Numerical simulation of cavitating flow in 2D and 3D inducer geometries

Abstract: A computational method is proposed to simulate 3D unsteady cavitating flows in spatial turbopump inducers. It is based on the code FineTurbo, adapted to take into account two-phase flow phenomena. The initial model is a time-marching algorithm devoted to compressible flow, associated with a low-speed preconditioner to treat low Mach number flows. The presented work covers the 3D implementation of a physical model developed in LEGI for several years to simulate 2D unsteady cavitating flows. It is based on a barotropic state law that relates the fluid density to the pressure variations. A modification of the preconditioner is proposed to treat efficiently as well highly compressible two-phase flow areas as weakly compressible single-phase flow conditions. The numerical model is applied to time-accurate simulations of cavitating flow in spatial turbopump inducers. The first geometry is a 2D Venturi type section designed to simulate an inducer blade suction side. Results obtained with this simple test case, including the study of its general cavitating behaviour, numerical tests, and precise comparisons with previous experimental measurements inside the cavity, lead to a satisfactory validation of the model. A complete three-dimensional rotating inducer geometry is then considered, and its quasi-static behaviour in cavitating conditions is investigated. Numerical results are compared to experimental measurements and visualizations, and a promising agreement is obtained. Copyright © 2004 John Wiley & Sons, Ltd.

On the relevance of kinematics for cavitation implosion loads

Abstract: This study presents a novel physical model to convert the potential energy contained in vaporous cavitation into local surface impact power and an acoustic pressure signature caused by the violent collapse of these cavities in a liquid. The model builds on an analytical representation of the solid angle projection approach by Leclercq et al. [“Numerical cavitation intensity on a hydrofoil for 3D homogeneous unsteady viscous flows,” Int. J. Fluid Mach. Syst. 10, 254–263 (2017)]. It is applied as a runtime post-processing tool in numerical simulations of cavitating flows. In the present study, the model is inspected in light of the time accurate energy balance during the cavity collapse. Analytical considerations show that the potential cavity energy is first converted into kinetic energy in the surrounding liquid [D. Obreschkow et al., “Cavitation bubble dynamics inside liquid drops in microgravity,” Phys. Rev. Lett. 97, 094502 (2006)] and focused in space before the conversion into shock wave energy takes place. To this end, the physical model is complemented by an energy conservative transport function that can focus the potential cavity energy into the collapse center before it is converted into acoustic power. The formulation of the energy focusing equation is based on a Eulerian representation of the flow. The improved model is shown to provide physical results for the acoustic wall pressure obtained from the numerical simulation of a close-wall vapor bubble cloud collapse.This study presents a novel physical model to convert the potential energy contained in vaporous cavitation into local surface impact power and an acoustic pressure signature caused by the violent collapse of these cavities in a liquid. The model builds on an analytical representation of the solid angle projection approach by Leclercq et al. [“Numerical cavitation intensity on a hydrofoil for 3D homogeneous unsteady viscous flows,” Int. J. Fluid Mach. Syst. 10, 254–263 (2017)]. It is applied as a runtime post-processing tool in numerical simulations of cavitating flows. In the present study, the model is inspected in light of the time accurate energy balance during the cavity collapse. Analytical considerations show that the potential cavity energy is first converted into kinetic energy in the surrounding liquid [D. Obreschkow et al., “Cavitation bubble dynamics inside liquid drops in microgravity,” Phys. Rev. Lett. 97, 094502 (2006)] and focused in space before the conversion into shock wave energy takes...