3D monolithic finite element approach for aero-thermics processes in industrial furnaces

The original publication is available at: http://www.esaim-proc.org/articles/proc/pdf/2011/04/proc113304.pdfInternational audienceWe consider in this paper a mathematical and numerical model to design an industrial software solution able to handle real complex furnaces configurations in terms of geometries, atmospheres, parts positioning, heat generators and physical thermal phenomena. A three dimensional algorithm based on stabilized finite element methods (SFEM) for solving the momentum, energy, turbulence and radiation equations is presented. An immersed volume method (IVM) for thermal coupling of fluids and solids is introduced and detailed. It consists in considering a single 3D grid of the furnace and solving one set of equations for both fluid and solid with different thermal properties. A fast anisotropic mesh adaptation algorithm based on the variations of the level set function is applied to ensure an accurate capture of the discontinuities at the fluid-solid interfaces. The proposed method demonstrates the capability of the model to simulate an unsteady three dimensional heat transfers and turbulent flows in an industrial furnace with the presence of conducting solids. Temperature measurements were carried in different locations and are compared to the experimental results

Modélisation du procédé de chauffage de pièces dans un four industriel.

http://hdl.handle.net/2042/16654International audienceDans cet article, on considère un maillage unique de l'enceinte d'un four industriel et on utilise d'abord une technique d'immersion de domaines pour prendre en compte les différentes positions et géométries des pièces à chauffer. Par la suite, la thermique est calculée par des méthodes Eléments Finis de type P1 stabilisées, pour à la fois contrôler la convection forcée (au niveau des brûleurs) et les chocs thermiques dûs à la diffusion transitoire (au niveau des lingots). Ces méthodes de stabilisation de type SUPG et SCPG pour la convection dominante et de type GGLS pour la diffusion pure sont présentées et analysées. La vitesse de convection est calculée en résolvant les équations de Navier Stokes couplées faiblement avec la thermique = We present in this paper the thermal modelling for an industrial oven. We begin by considering a single grid of this oven and then, in order to take into consideration different positions and forms of the heated parts inside, an immersion technique for multi-domain problem is used. Different stabilised finite element methods will be presented, such as SUPG and SCPG for reducing spurious oscillations in convectiondominated diffusion problem (at the burner's level) and GGLS for thermal shock's treatment in transient conduction heat transfer (at ingot's level). The velocity field is computed by solving the Navier-Stokes equations coupled to heat equations

Numerical simulation of boiling during the quenching process

National audienceDuring the thermal modelling of the quenching process, different stages of boiling need to be treated, from nucleate boiling to generation and growth of a vapour film. The interface between each phase flow is determined using a level set method. Surface tension is evaluated using the continuum surface force. The proposed approach demonstrates the capability of the model to simulate detachment of a single bubble and the generation of film vapour from a heated source. A comparison between numerical and experimental results shows a good agreement.br/>See http://hal.archives-ouvertes.fr/docs/00/59/26/76/ANNEX/r_71D43983.pd

3D numerical solution for quenching process using an adaptative multiphase flows

We present in this paper the thermal modelling of the quenching process. Different stages of such process need to be treated, from nucleate boiling to generation and growth of a vapour film. The interface between each phase flow will be determined using a level set method. Surface tension is evaluated using the continuum surface force and a new method to compute the gradient directly at the nodes. The proposed method demonstrates the capability of the model to simulate detachment of a single bubble and the generation of film vapour from a heated source

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

A Taylor discontinuous Galerkin method for the thermal solution in 3D mold filling

International audienceIn continuity with the work of the authors, a Taylor discontinuous Galerkin method is introduced to solve the thermal problem in the context of the 3D mold filling by viscous incompressible fluid. This numerical scheme is designed to deal with the physical phenomena of shear and temperature dependent viscosity, viscous heat generation and heat transfer by conduction and convection. A mixed temperature/heat flux formulation is introduced which enables to capture high temperature gradients without any polluting oscillations of the solution. The temperature and the heat flux are interpolated by a constant per element (P0 element) and an explicit solution based on the recursive time derivation of the equations is described. This approach aims to simulate non-isothermal flows of viscous fluid with moving free surfaces and more particularly the injection molding process involving thermal shocks at the interface between the cold mold wall and the hot polymer. The extension of the method in the context of the mold filling problem is given and several examples are proposed. The thermal solver is coupled to the mechanical solver which is based on a first order mixed finite element method for the kinematic and the solution of a transport equation for the flow front motion description. The proposed 3D technic is validated with known solutions and it is compared to 2D calculation obtained by different approaches. In continuity with the work of the authors, a Taylor discontinuous Galerkin method is introduced to solve the thermal problem in the context of the 3D mold filling by viscous incompressible fluid. This numerical scheme is designed to deal with the physical phenomena of shear and temperature dependent viscosity, viscous heat generation and heat transfer by conduction and convection. A mixed temperature/heat flux formulation is introduced which enables to capture high temperature gradients without any polluting oscillations of the solution. The temperature and the heat flux are interpolated by a constant per element (P0 element) and an explicit solution based on the recursive time derivation of the equations is described. This approach aims to simulate non-isothermal flows of viscous fluid with moving free surfaces and more particularly the injection molding process involving thermal shocks at the interface between the cold mold wall and the hot polymer. The extension of the method in the context of the mold filling problem is given and several examples are proposed. The thermal solver is coupled to the mechanical solver which is based on a first order mixed finite element method for the kinematic and the solution of a transport equation for the flow front motion description. The proposed 3D technic is validated with known solutions and it is compared to 2D calculation obtained by different approaches

Finite element solution of the 3D mold filling problem for viscous incompressible fluid

International audienceA general solution for the 3D mold filling by incompressible viscous fluid is described. It is based on the combination of an extended flow solver and the solution of a transport equation governing the flow front position. The flow solver uses tetrahedral elements, a first order stable mixed velocity pressure formulation entering in the family of the MINI-element, and a global iterative solution. The characteristic function of the fluid domain is shown to follow a conservative law and the moving fluid description is transformed into a transport equation in the whole domain to be filled. An explicit discontinuous Taylor-Galerkin scheme is introduced to solve this fluid motion equation. This scheme is shown to be consistent and conservative. The calculated shape of the fountain flow front is compared to the reference one. The flexibility and the robustness of this approach is demonstrated through complicated flows and geometries examples

Comparaison de la fraction d'éjection ventriculaire gauche en scintigraphie CZT et IRM myocardique (protocole CONFIRM-SC)

Objectif principal : validation de la scintigraphie myocardique sur caméra CZT (CZT-SPECT) pour la mesure de la FEVG, en référence à l'IRM. Objectifs secondaires : comparaison des volumes VG, de la cinétique segmentaire, et de la quantification de la nécrose en scintigraphie. En outre : comparaison du Strain longitudinal (SL) échocardiographique et du Strain circonférentiel (SC) IRM à l'analyse visuelle de la cinétique segmentaire en IRM, en recherchant un seuil de normalité pour le SL et le SC segmentaires dans cette population ischémique. Patients et méthode : 48 patients SCA ST+ explorés par échocardigraphie, IRMm et CZT-SPECT après 40 jours (21-71). Résultats : Fraction d'éjection CZT-SPECT et IRMm : bonne corrélation (r-0,790, p<0,0001,), comme la comparaison CZT-SPECT/échocardiographie et IRMm/échocardiographie (r-0,792 et 0,838 respectivement, p<0,0001,). CZT-SPECT et échocardiographie sous estimaient les VTD et VTS par rapport à l'IRMm (VTD : r-0,646 et 0,373 respectivement, p<0,0001). Comparaison de l'analyse segmentaire de l'épaississement myocardique : bonne corrélation entre les 3 techniques (CZT-SPECT / IRMm 77,88%, échocardiographie /IRMm 75,5%, CZT-SPECT /échocardiographie 83,74%, p<0,0001). Comparaison des données de cinétique segmentaire : concordance satisfaisante entre CZT-SPECT, l'IRM et échocardiographie, incrémentielle de la base vers l'apex. Perfusion : bonne corrélation entre CZT-SPECT et IRMm pour la détection et la quantification de la nécrose myocardique (r-0,7429, p<0,0001). Strain longitudinal (SL ) global : bonne corrélation avec la mesure de la FEVG en IRMm et en échocardiographie (p-0,61 et 0,6327 respectivement, p<0,01). Un Strain longitudinal (SL) de -16 en échocardiographie, et un Strain circonférentiel (SC) de -9 en IRMm étaient les seuils entre segments sains et ischémiques ou lésés (p<0,0001), sans que le SL échocardiographique et le SC IRMm ne soient corrélées entre eux. La CZT-SPECT est un examen fiable pour la mesure de la FEVG. La CZT-SPECT et l'échocardiographie tendent à sous estimer le VTD par rapport à l'IRMm, et dans une moindre mesure le VTS. La concordance de la CZT-SPECT avec l'IRMm pour la recherche d'une séquelle de nécrose myocardique est également satisfaisante. Les valeurs de SL échocardiographique <-16 et du SC IRMm <-9 apparaissent comme les seuils entre segments ischémiques et sains.CLERMONT FD-BCIU-Santé (631132104) / SudocSudocFranceF

Stabilized finite element method for solving heat transfer and turbulent flow inside industrial furnaces

A mathematical and numerical model to design an industrial software solution able to handle real complex furnaces con gurations in terms of geometries, atmospheres, parts positioning, heat generators and physical thermal phenomena has been developed. A three dimensional algorithm based on stabilized nite element methods (SFEM) for solving the momentum [1], energy, turbulence and radiation equations is presented. An immersed volume method for thermal coupling of fuids and solids is introduced. It consists in considering a single 3D grid of the furnace and solving one set of equations for both uid and solid with di erent thermal properties which can reduce the computational costs. A level set function enables to de ne precisely the position and the interface of any objects inside the furnace and to provide homogeneous physical and thermodynamic properties for each subdomain. Furthermore, in order to ensure an accurate capture of the discontinuities that characterize the strongly heterogeneous domain, we resort to an anisotropic mesh adaptation algorithm based on the variations of the level set function. The proposed method demonstrates the capability of the model to simulate an unsteady three dimensional heat transfers and turbulent fows in an industrial furnace with the presence of conducting solid