Compressible Flow Modeling Occurring in a Depressurization Process

COMSOL European Conference 2017

pipe flow

V. Bruyere1, T. Paris2, F. Viry1, P. Namy1
1 SIMTEC, 8 rue Duployé, Grenoble, 38100 France
2 CEA DAM, Valduc, Is-sur-Tille, France


The depressurization process is the emptying of one tank to another one through a pipe network. In order to optimize the design of pipes and tanks, a good knowledge of the gas flow behavior is required. The modeling of compressible flows with a Mach number near 1 is quite challenging and simplifications are necessary to create an efficient numerical tool. Thus, a simple model is developed here, using COMSOL Multiphysics® and the “Non-Isothermal Pipe Flow” interface. A theoretical validation is made by confrontation with analytical results. Then, using experimental results in multiple configurations, the model is adjusted to make it predictive.

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Towards a Quantitative Prediction of Ice Forming at the Surface of Airport Runways

COMSOL European Conference 2017

piste aeroport

J. D. Wheeler1, M. Rosa2, L. Capobianco2, P. Namy1
1. SIMTEC, 8 rue Duployé, Grenoble, 38100, France
2. Groupe ADP - Laboratoire DIAMLX, 16 rue du Miroir, Roissy Charles de Gaulle, 95931, France


Anticipation of meteorological events such as ice forming is a key challenge to optimize the use of deicing/anti-icing products on airport runways. To obtain a predictive numerical tool of ice forming on the runways, Groupe ADP and SIMTEC developed a COMSOL Multiphysics® model, in which several physical phenomena contributing to the surface temperature variations of the runway are involved. Radiative exchanges occur from and to the atmosphere together with the solar radiations. Moreover, the underground thermal inertia has a key role as it varies depending on the season and the runway temperature of the previous days. At last, the wind is also a source of thermal variation because of the convection. A comparison with temperature measurement on the runway provides an evaluation of the model abilities. Whereas some phenomena contribution precision should be improved, the computation results are in agreement with the experimental measurements. Thanks to the numerical model, the different thermal contributions are gathered and the variation of the temperature is computed over time at the surface and in the different layers of the runway foundation.

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Numerical modeling of flow focusing: Quantitative characterization of the flow regimes

Physics of Fluids 2017

image aeropsray

V. Mamet1,2, P. Namy3, and J.-M. Dedulle1,3
1 Laboratoire des Materiaux et du Genie Physique (LMGP), Grenoble INP–CNRS, 38016 Grenoble, France
2 DBV Technologies, 92220 Bagneux, France
3 SIMTEC, 38100 Grenoble, France



Among droplet generation technologies, the flow focusing technique is a major process due to its control, stability, and reproducibility. In this process, one fluid (the continuous phase) interacts with another one (the dispersed phase) to create small droplets. Experimental assays in the literature on gas-liquid flow focusing have shown that different jet regimes can be obtained depending on the operating conditions. However, the underlying physical phenomena remain unclear, especially mechanical interactions between the fluids and the oscillation phenomenon of the liquid. In this paper, based on published studies, a numerical diphasic model has been developed to take into consideration the mechanical interaction between phases, using the Cahn-Hilliard method to monitor the interface. Depending on the liquid/gas inputs and the geometrical parameters, various regimes can be obtained, from a steady state regime to an unsteady one with liquid oscillation. In the dispersed phase, the model enables us to compute   e evolution of fluid flow, both in space (size of the recirculation zone) and in time (period of oscillation). The transition between unsteady and stationary regimes is assessed in relation to liquid and gas dimensionless numbers, showing the existence of critical thresholds. This model successfully highlights, qualitatively and quantitatively, the influence of the geometry of the nozzle, in particular, its inner diameter.

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Modeling of the Lithium Hydride Hydrolysis under Low Relative Humidity

International Journal of Hydrogen Energy 2017

mécanisme réactionnels hydrolyse LiH

A. Oury2, P. Namy2, JP Bellat3, E. Sciora3, R. Besnard1 
1 CEA Valduc, 21120 Is sur Tille France
2 SIMTEC, 8 rue Duploye 38100 GRENOBLE France
3 Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Universite Bourgogne Franche-Comte, 9 A. Savary, BP47870, 21078 Dijon, France



A reactional mechanism describing the hydrolysis of lithium hydride (LiH) under moist atmosphere is proposed and modeled. It involves the formation of lithium oxide (Li2O) at low vapor pressure and both lithium oxide and lithium hydroxide (LiOH) at higher vapor pressures, with diffusion of water in these layers. A numerical model based on this mechanism is implemented with COMSOL Multiphysics to simulate the hydrolysis of LiH particles in open system (constant water vapor pressure). Kinetic parameters such as rate constant of reactions and diffusion coefficient of water in Li2O and LiOH are first fitted against experimental data. The best agreements are obtained when the diffusion coefficient of water is 10 times higher in LiOH than in Li2O. The resulting model accurately predicts the hydrolysis rates experimentally measured for a wide range of water vapor pressures (0.3e17 Pa). The hydrolysis mechanisms are compatible with a Li2O production limited by water diffusion and a LiOH production governed by the kinetics. Finally, simulation suggest that the thickness of the Li2O layer does not depends much on the water vapor pressure whereas that of LiOH increases drastically at high water vapor pressures.

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Multiphysics Modeling of Pulsed Laser Welding

ICALEO 2016

Fluid Flow vs ACD

V. Bruyere2,  C. Touvrey1, P. Namy2 and N. Authier1
1CEA Valduc, 21120 Is sur Tille France
2SIMTEC, 8 rue Duploye 38100 GRENOBLE France

Laser beam welding is largely used in industrial manufacturing because of the advantages it provides, such as high-quality welds. Nevertheless, depending on the operating conditions, porosities or unwanted deformations can be produced during welding operations. In order to understand and control the responsible underlying mechanisms, numerical models are developed in a unique finite element formalism. All models are based on experimental characterizations. First of all, a thermal-hydraulic model is developed to predict the dimensions of the melted zones and the heataffected zones as well as the mechanisms of porosities formation for a Ti6VAl4 alloy. A thermal-mechanical model including metallurgical phase changes is then developed in order to predict the residual states of stress and strain. The heat source is calibrated with an optimization procedure based on thermal-hydraulic analysis. Indeed, an equivalent approach is used to reduce the computational time for thermal-mechanical computations. Finally, this model is applied to a study case and numerical results are discussed and compared with experimental data.

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Implementation of an Interferometric Sensor for Measuring the Depth of a Capillary Laser Welding

ICALEO 2016

Fluid Flow vs ACD

N. Authier1, A. Baptiste1, C. Touvrey1, V. Bruyere2,  and P. Namy2
1CEA Valduc, 21120 Is sur Tille France
2SIMTEC, 8 rue Duploye 38100 GRENOBLE France

The welding laboratory located at the Commissariat a l'Energie Atomique et Aux Energies Alternatives (CEA) Valduc center in France uses pulsed and continuous wave (CW) laser sources to assemble metallic parts of low thicknesses. This article discusses the results obtained by the recent implementation of the In-process Depth Meter (IDM) of PRECITEC keyhole depth measurement sensor in our laboratory. This distance measurement technology uses a Michelson interferometer adapted to the very special conditions of the laser beam welding. Micrographs of pulsed welding tests on 316L stainless steel, TA6V plane sheets butt joints are analyzed and compared to the inline collected signals. The system's ability to follow dynamically the formation of the keyhole into the molten metal is evaluated and compared to numerical models performed in the lab using the nite element COMSOL Multiphysics software.

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Electrical and Bubbly Flow Modeling of a Molten Salt Electrolysis Cell

COMSOL European Conference 2016

Fluid Flow vs ACD

A.Oury1, P. Namy1, A.M. Martinez2, K.S. Osen2 and A. Solheim2
1SIMTEC, 8 rue Duploye 38100 GRENOBLE France
2SINTEF Materials and Chemistry, Sem Saelands vei 12, 7465 TRONDHEIM, Norway

A laboratory-scale electrolysis cell for the recovery of metals is simulated with COMSOL Multiphysics. Two models are implemented: an electrical model simulating the current density (reaction rate) distribution at the electrodes and a laminar bubbly flow model which solves for the electrolyte velocity induced by gas bubble production at the anode. A parametric study on the mesh refinement, the anode-cathode distance (ACD) as well as the bubble diameter (Db) is carried out. Quite heterogeneous current distributions are simulated at the electrodes’ surface, with strong edge effect at the cathode. At the anode, a more uniform current is however obtained when increasing ACD. The bubbly flow model suggests that significant electrolyte convective motions between the electrodes are favoured for small values of both ACD and Db.

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Aerothermal Simulation of a Refrigerated Truck Under Open/Closed-Door Cycles

COMSOL European Conference 2015

airtruck

A. Oury1, P. Namy1, M. Youbi-Idrissi2
1 SIMTEC, GRENOBLE
2 AIR LIQUIDE, Jouy en Josas, France

Heat transfer inside a refrigerated truck is a key phenomenon that governs the temperature inside the truck and the regulation of the cooling system. Up to now, a lot of experimental studies ([Tso et al., 02]) have been carried out to assess the effect of opening the door and to minimize the external heat transfer with fan air curtain. Together with AIR LIQUIDE, the world leader in gases, technologies and services for Industry and Health, SIMTEC, a French COMSOL certified consultant company, has developed a numerical model in COMSOL Multiphysics® software to simulate the heat transfer phenomena occurring during the use of the refrigerated truck, considering both open- and closed-door periods. The model is based on a coupling between CFD (k-ε/k-ω models) and heat transfer. Comparison with experimental results shows a reasonable agreement in terms of temperature inside the volume and at some specified points. This work demonstrates the feasibility of using COMSOL to model non-isothermal turbulent flow.

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Numerical Characterizations of Viscoplastic Behavior of TA6V with Metallurgical Phase Change

COMSOL European Conference 2015

evolutionphase

Vincent Bruyère 2, Charline TOUVREY1, Patrick NAMY2
1 CEA Valduc, 21120 Is sur Tille
2 SIMTEC, 38100 GRENOBLE

In order to predict the residual mechanical state of assemblies during pulsed laser welding, mechanical and metallurgical behaviors of the materials need to be precisely characterized. Based on experimental data and analyses, a numerical model is developed in Comsol Multiphysics to take into account the predominant effects (metallurgy influence, viscoplastic behavior) identified for TA6V. To validate our implementation, experimental and numerical results are compared at different temperatures.

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A Phase Field Approach to Model Laser Power Control in Spot Laser Welding

COMSOL European Conference 2014

comparaison expérience/numérique

Vincent Bruyère 2, Charline TOUVREY1, Patrick NAMY2
1 CEA Valduc, 21120 Is sur Tille
2 SIMTEC, 38100 GRENOBLE

Spot laser welding is largely used in industrial manufacturing, especially in the case of small penetration depth. Unfortunately, welded joins are often polluted by porosities. The formation of porosities depends on complex thermo-hydraulic phenomena. To understand and control these mechanisms, the COMSOL Multiphysics software is used to model both the interaction and cooling stages of an isolated impact made with a Nd:YAG pulsed laser. The model is based on the Phase Field method in order to apprehend the evolution of the liquid-gas interface shape. The numerical results are compared to experimental characterizations for different operating conditions. At last, the benefic effect of the laser power control (pulse shaping) is demonstrated.

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Thermohydraulic modeling of pulsed laser welding

ICALEO 2013

laser welding

Vincent Bruyère 1, Charline TOUVREY1, Patrick NAMY2
1 CEA Valduc, 21120 Is sur Tille
2 SIMTEC, 38100 GRENOBLE

The major aim of this study is to increase our understanding of the link between operating parameters and thermo-hydraulic evolution in the welding area, in the case of an isolated impact made with a Nd:YAG pulsed laser on a thin Ti6Al4V sheet. Two numerical approaches are used to model both the interaction stage and the cooling one. During the interaction, the free surface behavior is precisely described by a moving mesh method (ALE method). The dependence between the interface temperature and the recoil pressure is discussed and a simplified approach is used. The keyhole collapse and the cooling stage are modeled by the phase field method (Eulerian method), which enables to consider the behavior of the gas trapped into the melting pool. Numerical calculations are compared to experimental characterizations (melted zone shape and defects position), in the case of relatively low laser power (inferior to 1000 W).

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Comparison between Phase Field and ALE Methods to model the Keyhole Digging during Spot Laser Welding

COMSOL European Conference 2013

laser welding

V. Bruyère1 , Charline TOUVREY1, Patrick NAMY2
1 CEA Valduc, 21120 Is sur Tille
2 SIMTEC, 38100 GRENOBLE

Nowadays, spot laser welding is a full-fledged part of industrial manufacturing and is routinely used due to its advantages. It generates very located temperature gradients, and therefore, induces small distortions in the pieces. The COMSOL Multiphysics software is used to model the interaction stage of an isolated impact made with a Nd:YAG pulsed laser. The free surface evolution has been precisely described with a moving mesh method (ALE method) by imposing the recoil pressure and the energy deposition as boundary conditions. The results have been compared with those obtained with a fixed mesh method (Phase Field method) for isothermal and thermal cases. A discussion is proposed to choose the more appropriate method to model this problem.

Keywords: Welding, ND : YAG pulsed laser, Thermo-hydraulic, ALE, Phase-Field method.

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Modélisation de la formation des défauts de type porosité lors du soudage de matériaux métalliques par laser impulsionnel

Séminaire CNRS Européen Recherche/Industrie Laserap'7

laser welding

Charline TOUVREY1, Patrick NAMY2, Céline COSSU1
1 CEA Valduc, 21120 Is sur Tille
2 SIMTEC, 38100 GRENOBLE

Le procédé de soudage par laser impulsionnel permet d'assembler des pièces métalliques par une succession d’impacts, produisant chacun une fusion localisée de la matière. À la fin de l’impact laser, les phases de remplissage du capillaire et de solidification du métal liquide se succèdent. Des bulles de gaz emprisonnées dans le bain de soudage peuvent alors conduire à la formation de porosités. Afin d’améliorer notre compréhension du lien entre les propriétés thermophysiques des métaux et les risques de formation des défauts, un modèle numérique reliant les caractéristiques géométriques du bain fondu et la durée de remontée des bulles de gaz a été élaboré au sein du code COMSOL. Ce modèle se borne à représenter les phénomènes physiques après l’arrêt du faisceau laser, une fois le capillaire de soudage rempli. Le calcul prend en compte la remontée des bulles sous l’effet de la poussée d’Archimède, l’influence de la tension de surface, et l’avancée du front de solidification liée au refroidissement (calcul thermohydraulique couplé). Des calculs ont été menés pour deux matériaux, le tantale et l’alliage de titane TA6V, pour différentes tailles initiales de bulles.

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Formation of Porosities During Spot Laser Welding of Tantalum

COMSOL European Conference 2011

laser welding

C. Touvrey1 , and P. Namy2
1 CEA Valduc, Is-sur-Tille, France
2 SIMTEC, Grenoble, France

The aim of the study is to predict the formation of porosities in the case of spot laser welding of tantalum. During the interaction, a deep and narrow cavity, called the keyhole, is generated. At the end of the interaction, surface tension provokes the collapse of the keyhole. Gas bubble can then be trapped into the melting pool, and give birth to residual porosities, according to the solidification time.

A model has yet been developed to simulate keyhole collapse. This model was presented at the last COMSOL European conference. The purpose of the present study is to simulate the bubble up rise. The problem is especially complex due to the high surface tension of the liquid tantalum (2.1 N.m-1).

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Comparison Between Honeycomb and Fin Heat Exchangers

COMSOL European Conference 2011

honeycombP. Gateau1 , P. Namy2 , and N. Huc3
1 SAS SYNGAS, Saint Viaud, France
2 SIMTEC
, Grenoble, France
3 COMSOL, Grenoble, France

Metal honeycombs are used as catalyst supports. They can be considered as complex fins for heat exchange. A simple heat transfer model was compared with 2D simulations using COMSOL Multiphysics. There was a good correlation when the fluid temperature was the same in all cells. However, significant discrepancy apperared when compared with a 3D simulation with laminar flow.

Honeycomb cells produced a temperature gradient which reduced the heat transfer. The radiant transfer was also investigated using 2D simulation. Modeling using COMSOL revealed the drawbacks of using honeycombs in steam reforming reactors. 3D modeling showed that a careful representation of the inlet was needed for realistic results.

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Finite Element Analysis of Cables Heating Due to PoE/PoE+

COMSOL European Conference 2010

 

Temperature distribution within a cable bundle used to consider realistic geometries of the bundle .S. Francois1, and P. Namy2
1Nexans Research Center, Lyon cedex, France
2SIMTEC, Grenoble, France

Power over Ethernet (PoE/PoE+) is a technology allowing to transmit data and power over the same data cable. The major concern for this technology is the degradation of data transmission performances due to the temperature increase in the cable. To have a better quantitative and qualitative knowledge of the temperature field in the cables, Nexans has developed a 2D finite element thermal model thanks the software COMSOL Multiphysics. In this model, the heat source is due to the joule effect, depending on the intensity level. This thermal model enables us to take into consideration several configurations of cable bundles and to optimize the temperature field thanks to cable design.

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Level Set Method for Fully Thermal-Mechanical Coupled Simulations of Filling in Injection and Micro-Injection Molding Process

COMSOL European Conference 2009

Vortices in the air domain.M. Moguedet1, R. Le Goff1, P. Namy2, and Y. Béreaux3
1Pôle Européen de Plasturgie, Bellignat, France
2SIMTEC, Grenoble, France
3INSA de Lyon, Site de Plasturgie, Bellignat, France


In this work we tackle a more theoretical aspect of micro-injection molding, to better understand physics during the process, through numerical simulations of cavity filling. We developed a two phase flow approach by the use of COMSOL Multiphysics®. In a first step, a Level Set model is applied to several configurations: Newtonian and non Newtonian fluid (Cross viscosity law), coupled with a thermal equation and a thermal dependence of the viscosity (Williams-Landel-Ferry law). We take into account the unsteady thermal behavior of the mould while injecting the polymer into the cavity. Finally, as air –trapping often occurs in the injection molding process, we present some results considering a pseudocompression law (low Mach number) for the air. To conclude, we show the ability of the COMSOL model to simulate polymer filling in microfeatures.

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On the Use of COMSOL Multiphysics to Understand and Optimize the Filling Phase in the Injection and Micro-Injection Molding Process

COMSOL European Conference 2007

Newtonian front profile at t=0.01 s

M. Moguedet1, P. Namy2, and Y. Béreaux3
1Pôle Européen de Plasturgie, Bellignat, France
2SIMTEC, Grenoble, France
3
LAMCOS, Site de Plasturgie, INSA Lyon, Bellignat, France

The work presented here deals with the simulation of the cavity filling stage of the injection and micro-injection molding process for thermoplastic materials. COMSOL Multiphysics gives us the means to take into consideration some other aspects usually neglected in commercial 3D softwares dedicated to polymer processing. In particular, tracking of the flow front is based on a Level Set approach. Results are presented for a Newtonian and non-Newtonian polymer, and in an isothermal or thermal dependant configuration. The calculations are compared to experimental results on a polypropylene.

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Convective Movements in an Electrolyser

COMSOL European Conference 2007

 

Convective Movements in an ElectrolyserB. Morel1, P. Namy2, C. Belhomme1, and I. Crassous3
1Comurhex, Pierrelatte, France
2SIMTEC, Grenoble, France
3LI2C, Paris, France

Modeling electrolysers is a challenge because of the strong coupling between electrical, thermal and CFD equations. Indeed the electrical conductivity of the electrolyte varies with the temperature, which in turn depends on the heat dissipated by the Joule effect and anode over-voltage.In the present study, the fluid velocity values are computed near the electrodes using a diphasic level set model, but the full calculations are performed using a monophasic model. Our goal is to evaluate the relationship between the average temperature of the cell and the average current for a given cooling surface.

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