HPC large scale simulation of an industrial fluidized bed and applications to chemical engineering processes with NEPTUNE_CFD

Fluidized beds and more broadly dilute and dense particle-laden reactive flows are encountered in a wide range of industrial chemical engineering applications such as catalytic polymerization, coal combustion … Nowadays, it is possible to perform realistic 3D simulations of industrial configurations using an unsteady Eulerian multi-fluid approach for polydisperse reactive flows with a good physical modelling. Hence CFD is a powerful tool for studying the optimization of chemical processes, new designs and scaling-up. To obtain numerical results in an acceptable CPU time, it is important to check the feasibility of CFD simulation of fluidized bed flows in complex geometries at industrial scale. Also we need to estimate HPC capacities of CFD tools. Numerical simulations have been performed with the solver NEPTUNE_CFD: parallelized unstructured code (MPI) using unsteady Eulerian multi-fluid approach. NEPTUNE_CFD is based on the same numerical methods than Code_Saturne. Code_Saturne is an open source CFD software code ready to run on petascale machines. NEPTUNE_CFD’s high parallel computing performances for particle-laden flows have been demonstrated over last years. Recent developments allow overtaking NEPTUNE_CFD’s limitations making it fit for massive parallel computing. Please click Additional Files below to see the full abstract

Numerical simulation of unsteady dense granular flows with rotating geometries.

In chemical engineering applications, it is not uncommon to encounter reactors featuring rotating parts. As these rotating parts are present in order to enhance processes such as chemical reactions and/or ensure homogeneity, it is essential to take them into account to perform predictive numerical simulations. This aspect can be particularly challenging, even more so when complex industrial geometries are to be treated.In this paper a numerical methodology for simulating unsteady granular flow in rotating geometries is presented. The method is based on splitting the domain into static and rotating parts. The information between rotating and static parts is passed by a non-conformal mesh matching technique. The presented methodology is validated numerically by comparing its results with other conventional methods. The method is then applied to an industrial scale problem. The applicability of the method and the way it may be used to investigate complex flow is demonstrated. Therefore this approach enables to consider the full geometry of complex reactors. It opens the door to further investigation, optimization and design of industrial scale chemical processes

Computational study of dense granular flows in stirred reactors

In chemical engineering applications, reactors featuring rotating parts are common practice. As these rotating parts are present in order to enhance chemical reactions, it is essential to take them into account when performing predictive numerical simulations. This aspect can be particularly challenging, even more so when complex industrial geometries are to be treated. In this communication the rotating mesh numerical methodology of NEPTUNE_CFD V3.0 (an Eulerian n-fluid multiphase flow CFD code) is presented. The method is based on splitting the domain into static and rotating parts. The information between rotating and static parts is passed thanks to a non-conformal mesh matching technique. The methodology is first validated, both numerically and experimentally using the classical rotating drum case. The high degree of compaction of the flow is taken into account thanks to a frictional stress tensor. The method is then pushed further and used to investigate the hydrodynamics of dry granular beds in stirred vessels. The results show that the rotating mesh method can effectively treat such configurations, hence offering interesting insight concerning the dynamics of the flow

Massively parallel numerical simulation using up to 36,000 CPU cores of an industrial-scale polydispersed reactive pressurized fluidized bed with a mesh of one billion cells

For the last 30 years, experimental and modeling studies have been carried out on fluidized bed reactors from laboratory up to industrial scales. The application of developed models for predictive simulations has however been strongly limited by the available computational power and the capability of computational fluid dynamics software to handle large enough simulations. In recent years, both aspects have made significant advances and we thus now demonstrate the feasibility of a massively parallel simulation, on whole supercomputers using NEPTUNE_CFD, of an industrial-scale polydispersed fluidized-bed reactor. This simulation of an olefin polymerization reactor makes use of an unsteady Eulerianmulti-fluid approach and relies on a billion cellsmeshing. This is a worldwide premiere as the obtained accuracy is yet unmatched for such a large-scale system. The interest of this work is two-fold. In terms of High Performance Computation (HPC), all steps of setting-up the simulation, running it with NEPTUNE_CFD, and post-processing results induce multiple challenges due to the scale of the simulation. The simulation ran using 1260 up to 36,000 cores on supercomputers, used 15 millions of CPU hours and generated 200 TB of rawdata for a simulated physical time of 25s. This article details the methodology applied to handle this simulation, and also focuses on computation performances in terms of profiling, code efficiency and partitioning method suitability. Though being by itself interesting, the HPC challenge is not the only goal of this work as performing this highly-resolved simulation will benefit chemical engineering and CFD communities. Indeed, this computation enables the possibility to account, in a realistic way, for complex flows in an industrial-scale reactor. The predicted behavior is described, and results are post-processed to develop sub-grid models. These will allow for lower-cost simulations with coarser meshes while still encompassing local phenomenon

Contribution à la modélisation instationnaire et tridimensionnelle du comportement dynamique de l'arc dans une torche de projection plasma

Ce travail, mené dans le cadre d'une collaboration avec le CEA-DAM du Ripault et le laboratoire Mécanique des Fluides et Transferts Thermiques d'EDF, porte sur la modélisation 3D et instationnaire du comportement de l'arc électrique et de la formation du jet de plasma dans une torche de projection plasma. Après avoir rappelé les différents modes de fonctionnement de ce type de torche : mode stationnaire, mode fluctuant et mode de claquage-réamorçage, nous détaillons la structure de l'arc électrique, et, en particulier, les zones cathodiques et anodiques. Puis, nous résumons les principaux modèles numériques proposés dans la littérature pour simuler le comportement de l'arc dans la tuyère. Cette revue permet de définir les hypothèses les plus couramment formulées pour étudier les arcs électriques : E.T.L., fluide newtonien, écoulement laminaire, incompressible et stationnaire, plasma optiquement mince. Nous présentons ensuite la formulation mathématique du modèle magnéto-hydrodynamique 3D et instationnaire mis en œuvre pour décrire l'interaction entre l'écoulement de gaz et l'arc électrique, ainsi que les principales hypothèses et conditions aux limites que nous avons utilisées. Dans ce modèle, le claquage de l'arc repose sur une valeur limite Ec du champ électrique local alors que le réamorçage est réalisé grâce à une colonne chaude imposée dans la zone de la tuyère où la valeur locale du champ électrique dépasse la valeur de consigne Ec. Les équations du modèle sont résolues à l'aide de la chaîne logicielle ESTET 3.4. Ce modèle prédit bien de façon qualitative le comportement dynamique de l'arc, en particulier en fonction de la nature du gaz plasmagène ; il conduit à des températures et vitesses de gaz en sortie de tuyère présentant un accord raisonnable avec celles déterminées expérimentalement. Par contre, il surestime la tension d'arc et les dimensions de la tacheLIMOGES-BU Sciences (870852109) / SudocSudocFranceF

La mémoire du désir (poétique du temps et figuration du sujet dans l'Histoire de ma vie de Giacomo Casanova)

Ce qu il y a de plus profond en l homme, c est la peau en tant qu il se connaît écrit Paul Valéry dans L Idée fixe. Peu d œuvres autobiographiques se sont pourtant abandonnées à l exploration de cette profondeur : depuis Rousseau, les impératifs du genre exigent d aller in cute. L Histoire de ma vie est de ce petit nombre. Casanova, longtemps l homme de toutes les superficialités, parcourt sans discontinuer cette surface de l être, non pour s y oublier, mais justement en tant qu il se connaît . Sur l épiderme, s affichent les plus vertigineuses métamorphoses autant que se dévoilent les plus éclatantes révélations : l homme y découvre de quelle étoffe il est fait. La réflexivité du récit de soi ne saurait faire l économie de cette médiation, et ce que tente de retrouver l écrivain au fil des pages, c est moins une vérité ou une essence qu un corps à nouveau capable de profondeur. L œuvre tend à recomposer ses tissus, à rétablir sa splendeur et à rejouer ses élans, espérant ainsi triompher de la seule réalité véritablement superficielle : le Temps. La mémoire du désir renvoie à cette anamnèse charnelle, qui se déploie à l écart de la conscience et de l intériorité mais au sein du théâtre des peaux et des parures. L Histoire de ma vie tente d en recueillir et d en relancer l intensité, de redonner au sujet écrivant cette chair perdue, la seule qu il connaisse et que chaque ligne tente de reconquérir. Cette mémoire à sa temporalité propre, elle façonne un sujet inédit et génère un régime d écriture singulier : elle ouvre ainsi au sein de l univers des écritures du Moi un espace immense et encore insuffisamment exploré.What is deepest in man, it is the skin - as he knows himself," wrote Paul Valéry in L idée fixe. Few autobiographical works have quite explored of this depth: since Rousseau, the imperatives of the genre require to go in cute. L Histoire de ma vie belongs to this little number. Casanova, for long man of all superficialities, runs continuously the surface of being, not to forget himself, but precisely "as he knows himself." On the epidermis, appear the most dizzying metamorphoses as the most brilliant revelations: man discovers of what stuff is made. The reflexivity of the narrative itself cannot do without this mediation, and that the writer tries to find as the pages go by, it's less a truth or essence than a body again capable of depth. The work tends to recompose its tissues, to restore its splendor and to replay his impulses, hoping to overcome the only truly superficial reality: Time. Desire s memory refers to this carnal anamnesis, which unfolds away from consciousness and interiority but in the theater of skins and ornaments. L Histoire de ma vie tries to collect and to raise the intensity, giving back to the subject writing this flesh lost, the only one he knows and that each line is trying to regain. This memory has its own temporality; it shapes a unique subject and generates a unique writing system: it opens within the world of writing of the self an immense space and still insufficiently explored.LYON3-Bibliothèques (693872102) / SudocSudocFranceF

Toward Active-Site Compression in Rigid-Rod ß-Barrels

Applying the Woodhull equation to organic chemistry, a concept to maximize remote control of chemical processes that take place within synthetic multifunctional pores is described

Synthesis of {242}- and {323}-p-Octiphenyls

The introduction of rigid-rod molecules as privileged scaffolds has opened routes to otherwise problematic supramolecular architecture like artificial ß-barrels and functional supramolecules covering pores, hosts, sensors, and catalysts. The usefulness of p-oligophenyls for the construction of functional barrel-stave architecture has, however, been limited by uniform substitution along the rigid-rod scaffold. The objective of this report is to overcome this obstacle for the synthesis of p-octiphenyls with orthogonally protected carboxylic acid groups along the rigid-rod scaffold. In the reported {242}-p-octiphenyl 1, the two peripheral arene moieties carry carboxylic acid groups protected as benzyl esters, whereas the four central carboxylic acid groups are protected orthogonally as tert-butyl esters (Scheme 2). The complementary orthogonal protection of the three peripheral and the two central arenes is achieved in the {323}-p-octiphenyl 2 (Scheme 3). The realized {242}- and {323}-p-octiphenyls 1 and 2, respectively, provide a complete set for the general access to refined rigid-rod barrel-stave architecture with maximized functional plasticity. The need for resolution-enhanced (aliased) HMBC 2D-NMR spectroscopy to characterize these refined oligomers is described in the following publication in this issue of Helv. Chim. Acta

Synthesis of {323}-p-Octiphenyls: Orthogonal Functionalization along a Rigid-Rod Scaffold for Refined Supramolecular Architecture

The synthesis of p-octiphenyls carrying orthogonal tert-butyl esters in the peripheral positions 1(2), 2(2), 3(3), 6(2), 7(3), and 8(2) and either p-methoxybenzyl or benzyl ester substituents in the central positions 4(2) and 5(3) is described. Resolution-enhanced HSQC/HMBC two-dimensional NMR spectroscopy is implemented as an attractive method for the complete characterization of complex p-oligophenyl scaffolds