Mesocale approach for fluidized beds

Fluid-particle flows are frequently encountered in industrial facilities and especially in chemical engineering processes. In this work, we focus on fluidized beds, which involve a fluid flow passing upward through a pack of particles with such a velocity that the fluid force acting on particles is larger than their weight

The Triptych Tetrad: Marshall McLuhan\u27s Neo-Medieval Communication Theory

The work of Marshall McLuhan has often been reduced to the form of catchphrases and McLuhanisms, such as the global village and the medium is the message in the field of communication. Though these phrases capture an aspect of his thought, the scholarly understanding of McLuhan\u27s vision remains incomplete, even within the specialized area of Media Ecology, of which McLuhan is recognized as the intellectual father. Throughout his corpus, McLuhan makes reference to the classical and medieval trivium, which was the basis for education throughout Western history until the Renaissance. Indeed, he developed a history of the trivium up to the Renaissance in order to understand the works of Thomas Nashe. At the end of his life, he worked to synthesize his views on technology, media, and communication, and the arts of the trivium-- grammar, logic, and rhetoric--which were essential to these works. Consequently, this project details the connection between the classical and medieval trivium and McLuhan\u27s tetrad, which was the heuristic tool that advanced as New Science for the twentieth and twenty first centuries. By detailing this connection, the tetrad is a tool that advances a neo-Medieval theory of communication. In its essence, the neo-Medieval communication theory is attentive to the linguistic essence of the cosmos, is attentive to the transformative nature of understanding, and unifies the human person within a perceptual and poetic understanding of the world

Interpersonal Rhetoric: An Approach to Bettering Oneself and Others

Although interpersonal interaction is predominantly studied through the lens of communication studies, the field was originally studied primarily by scholars of rhetoric. Though this paradigm was instrumental in the founding of interpersonal communication, interpersonal rhetoric has largely been ignored by the discipline. However, throughout the last few decades, a few scholars have attempted to reinvigorate the study of interpersonal communication through the lens of rhetoric. This paper explores the several key concepts and perspectives within the history of the rhetorical approach to interpersonal communication, i.e., interpersonal rhetoric

Editorial Viscoplastic fluids: From theory to application 2013

International audienceq This issue of the Journal of Non-Newtonian Fluid Mechanics includes a series of papers based on work presented at the international workshop on Viscoplastic fluids: from theory to application, held Nov. 18–21, 2013 in Rueil Malmaison, France. A list of participants is provided in Table 1. This was the fifth biannual meeting on this subject. The previous meetings were held in Banff (Alberta, Canada), Monte Verita (Ascona, Switzerland), Limassol (Cyprus) and Rio de Janeiro (Brasil) [1]. Like previous editions, the aim of the workshop was to bring together leading researchers in the field of viscoplastic fluids across several disciplines to foster the awareness and the transfer of ideas, both from academic research and industry. The program consisted in a single technical session and three invited keynote lectures. A total of 49 talks and 9 posters were presented, spanning fascinating topics from the coating of a viscoplastic fluid on a plate to the numerical simulation of the transition of viscoplastic fluid flows to turbulence. The workshop enjoyed an unprecedented number of 80 participants (Fig. 1), a popularity that emphasizes that viscoplastic fluids are a ''hot'' topic in the field of non-Newtonian Fluid Mechanics. Invited speakers were John Tsamopoulos (University of Patras, Greece), Guillaume Ovarlez (Laboratoire Navier, Université Paris-Est, France) and Fabrice Toussaint (Lafarge Centre de Recherche, France). John Tsamopoulos opened the meeting with an invited talk on the numerical simulation of yield stress fluid flows and its applications to the problem of the rising of a single bubble. He both elaborated on the technical details of the numerical tools available nowadays for the simulation of this class of flows and provided insight on the effect of elasticity and pressure oscillations. On the second day of the workshop, Guillaume Ovarlez gave an overview on the rheological behavior of suspen-sions of particles and bubbles in a yield stress fluid, illustrating his findings with a large number of experimental results. On the third day, Fabrice Toussaint bridged academic research and industrial concerns in the field of concrete rheometry, ranging from the fundamental behavior of concrete slurries and their characterization in rheometers to the fascinating last i-Phone application designed to tell the truck driver how quick the concrete slurry properties are evolving in the truck's rotating drum while driving to the construction site. Standard talks ranged from experiments, theory to numerical simulations, with an emphasis on the rheolo-gical behavior of carbopol gels and the more general question of how to experimentally characterize yield stress materials with thixotropy, a question that has been mobilizing the attention of the yield stress community for a few decades. The realistic and accurate modelling of the behavior of viscoplastic and thixotropic materials still remains an unsolved question in the field, as already underlined two years before in Rio de Janeiro, but also progress has been made, with new measurement techniques as, e.g., low amplitude oscillatory shear (LAOS). In particular, the workshop featured intense discussions on thixotropy and its mathematical modelling. Efforts in designing new numerical approaches with enhanced accuracy and fast convergence have seemed to slow down and the workshop was an occasion to collectively acknowledge that this research direction should be revived. The workshop took place at IFPEN-Rueil Malmaison, in the suburb of Paris, France. IFPEN is a large national research center in the field of energy, with nice facilities and well designed services. The social program started with an ice-breaking cocktail in a French-style coffee shop named ''Café Leffe'' in the heart of Rueil Malmaison, which was a casual occasion to chat with long-term colleagues and enables new participants to VPF to immerse into the yield (no) stress community and yield to the pleasure of enjoying French wines and the warm and friendly atmosphere o

Controlling the Quality of Two-Way Euler/Lagrange Numerical Modeling of Bubbling and Spouted Fluidized Beds Dynamics

We numerically simulate three-dimensional fluidized beds of monodisperse spheres using a two-way Euler/Lagrange method. Particles trajectories are tracked in a Lagrangian way, and particles collisions are computed by a soft sphere model. The fluid conservation equations are written in a classical Eulerian fashion and are locally averaged on cells 1 order of magnitude larger than particles. We detail the equations of the model and their numerical implementation. We study the influence of numerical parameters and simulation domain size on computed results in a biperiodic fluidized bed. We then validate the model against theoretical results for a bubbling fluidized bed and against experimental data for a single- and multi-nozzle spouted bed. Finally, we investigate the influence of the Coulomb friction coefficient magnitude on a single-nozzle spouted bed dynamics in order to emphasize the importance of tangential friction in such processes

Fluidization of irregular particles - Part II: A particle-resolved simulation method to model hydrodynamic interactions

Irregular particle shapes are ubiquitous in many real-life systems and in particular in the chemical engineering industry. Most of the corresponding numerical simulations are carried out using spherical particles due to the lack of appropriate numerical methods at the particle level or appropriate closure laws for hydrodynamic and collisional interactions in Euler-Lagrange and Euler-Euler models. Since in Part I, we presented a numerical technique implemented in our granular code Grains3D to treat the collisional behaviour of particles of (almost) arbitrary shape, we are now in a favourable position to suggest a corresponding Particle-Resolved Simulation (PRS) method to which Grains3D is coupled to (1,2,3). It is based on a Distributed Lagrange Multiplier/Fictitious Domain technique combined with Finite Volume/Staggered Grid discretization (2,3), that supplies solutions of satisfactory accuracy. This study aims to go one step further and to extend our numerical method to non-convex particles. This extension is implemented in our parallel numerical platform PeliGRIFF (4) . We illustrate the novel simulation capabilities of PeliGRIFF on the problem of the fluidization of trilobic/quadrilobic particles encountered in Oil & Gas catalytic reactors. First, we assess the space convergence and overall accuracy of the computed solution in the case of the flow past an infinite array of trilobes/quadrilobes. Then, we show results of the flow through a fixed bed made of trilobes/quadrilobes at random loose packing. Finally, we present preliminary results relevant to an actual fluidization. In conclusion, we discuss the computing challenges of these simulations and the integration of their results in a comprehensive multi-scale approach. REFERENCES A. Wachs. A DEM-DLM/FD method for direct numerical simulation of particulate flows: Sedimentation of polygonal isometric particles in a Newtonian fluid with collisions. Computers & Fluids, 38, 1608-1628, 2009. A. Wachs, A. Hammouti, G. Vinay, M. Rahmani. Accuracy of Finite Volume/Staggered Grid Distributed Lagrange Multiplier/Fictitious Domain simulations of particulate flows. Computers & Fluids, 115, 154-172, 2015. F. Dorai, C. Moura Teixeira, M. Rolland, E. Climent, M. Marcoux, A. Wachs. Fully resolved simulations of the flow through a packed bed of cylinders: Effect of size distribution. Chemical Engineering Science, 129, 180-192, 2015. PeliGRIFF, A multi-scale numerical modeling tool for fluid/particles flows. http://www.peligriff.co

Coupling the fictitious domain and sharp interface methods for the simulation of convective mass transfer around reactive particles: towards a reactive Sherwood number correlation for dilute systems

We suggest a reactive Sherwood number model for convective mass transfer around reactive particles in a dilute regime. The model is constructed with a simple external-internal coupling and is validated with Particle-Resolved Simulation (PRS). The PRS of reactive particle-fluid systems requires numerical methods able to handle efficiently sharp gradients of concentration and potential discontinuities of gradient concentrations at the fluid-particle interface. To simulate mass transfer from reactive catalyst beads immersed in a fluid flow, we coupled the Sharp Interface Method (SIM) to a Distributed Lagrange Multiplier/Fictious Domain (DLM/FD) two-phase flow solver. We evaluate the accuracy of our numerical method by comparison to analytic solutions and to generic test cases fully resolved by boundary fitted simulations. A previous theoretical model that couples the internal diffusion-reaction problem with the external advection-diffusion mass transfer in the fluid phase is extended to the configuration of three aligned spherical particles representative of a dilute particle-laden flow. Predictions of surface concentration, mass transfer coefficient and chemical effectiveness factor of catalyst particles are validated by DLM-FD/SIM simulations. We show that the model captures properly the effect of an internal first order chemical reaction on the overall respective reactive Sherwood number of each sphere depending on their relative positions. The proposed correlation for the reactive Sherwood number is based on an existing non-reactive Sherwood number correlation. The model can be later used in Euler/Lagrange or Euler/ Euler modelling of dilute reactive particle-laden flows

Mass transfer towards a reactive particle in a fluid flow: Numerical simulations and modeling

We study mass transfer towards a solid spherical catalyst particle experiencing a first order irreversible reaction coupled to an external laminar flow. Internal chemical reaction and convective-diffusive mass transfer in the surrounding fluid flow are coupled by concentration and flux boundary conditions at the particle surface. Through this coupling, the mean particle surface and volume concentrations are predicted and the internal/external Sherwood numbers are obtained. We investigate the interplay between convection, diffusion, and reaction by computational fluid dynamics and establish a model for the mass transfer coefficient accounting for diffusion and internal first-order chemical reaction. We obtain a prediction of the mass transfer coefficient through mass balance or using the classical additivity rule. The model is numerically validated by fully resolved numerical simulations over a wide range of Reynolds number, Schmidt number and Thiele modulus which shows that assuming decoupled treatment of external and internal mass transfer gives very accurate predictions. Finally, we test the unsteady response of the model. The model predicts the evolution of the mean volume concentration for a particle placed in a steady convective-diffusive stream. Predictions of the unsteady model are in very good agreement with computed results