Modelling Dispersed Two-Phase Flows: Closure, Validation and Software Development

1994 ◽  
Vol 47 (6S) ◽  
pp. S80-S84 ◽  
Author(s):  
P. L. Viollet ◽  
O. Simonin

Closure for the Eulerian modelling of two-phase flows have been developed, based upon extensions of the theory of Tchen of the dispersion of particles in homogeneous turbulence. This model has been validated using large-eddy simulation of homogeneous turbulence, jets loaded with particles, and bubbly flows. In addition with k-epsilon model for the continuous phase, and closures for the Reynolds stresses of the dispersed phase, this theory has been implemented in 2D and 3D software solving the Eulerian two-phase equations (Me´lodif in 2D, as a research code, and ESTET-ASTRID in 3D). These softwares have been applied to complex situations of industrial interest.

2019 ◽  
Vol 208 ◽  
pp. 115156 ◽  
Author(s):  
Mohammad Haji Mohammadi ◽  
Fotis Sotiropoulos ◽  
Joshua R. Brinkerhoff

Author(s):  
Olivier Simonin ◽  
Kyle D. Squires

Numerical simulation continues to evolve as an important tool in the analysis and prediction of two-phase turbulent flows. Computations are playing an increasingly important role as both a means for study of the fundamental interactions governing a process or flow, as well as forming the backbone for engineering predictions of physical systems. At a practical level, computations for engineering applications continue to rely on solution of a statistically-averaged equation set. Many of the statistical correlations requiring closure in Reynolds-averaged models are often difficult or impossible to measure in experimental investigations of two-phase flows. Computational techniques that directly resolve turbulent eddies are an important component in evaluating closure models, while at the same time offering a useful approach for basic studies of fundamental interactions. The focus of the lecture is on numerical prediction and study of turbulent two-phase flows using computational techniques such as Large Eddy Simulation (LES) that directly resolve the large, energy-containing scales of the turbulent motion. Within this broad class, the subset of two-phase flows in which a dispersed phase is comprised of small particles and is present at low volume fractions is of primary interest, using Lagrangian computational techniques for the prediction of trajectories of a large ensemble of discrete particles. The scope of such an approach considered is on systems in which the ensemble comprising the particulate phase is large enough that direct resolution of the flow in the vicinity of each particle is not feasible and, consequently, models on fluid-particle interfacial transfer and particle-particle interaction must be imposed. The focus of the lecture is on numerical prediction and study of turbulent two-phase flows using computational techniques such as Large Eddy Simulation (LES) that directly resolve the large, energy-containing scales of the turbulent motion. Within this broad class, the subset of two-phase flows in which a dispersed phase is comprised of small particles and is present at low volume fractions is of primary interest, using Lagrangian computational techniques for the prediction of trajectories of a large ensemble of discrete particles. The scope of such an approach considered is on systems in which the ensemble comprising the particulate phase is large enough that direct resolution of the flow in the vicinity of each particle is not feasible and, consequently, models on fluid-particle interfacial transfer and particle-particle interaction must be imposed. The advantages and limitations of such a technique are first considered and its accuracy is evaluated by comparison with discrete particle simulations coupled with fluid turbulence predictions obtained using DNS (understood in the present context as solution of the carrier-phase flow without the use of explicit subgrid turbulence models). An overview and examples of the application of LES to prediction and scientific study of dispersed, turbulent two-phase flows is then presented for several representative flow configurations: statistically stationary and decaying particle-laden isotropic turbulence, homogeneous shear flow, fully-developed turbulent channel flow, and turbulent particle-laden round jet. In such flows, the detailed description possible using LES enables in-depth evaluations of statistical and structural features. In particular, the role of inter-particle collision in turbulent channel flow and more recent efforts focused on exploration and analysis of the spatial structure of the particle concentration and velocity fields in homogeneous turbulence are discussed.


Author(s):  
Enrica Masi ◽  
Benoiˆt Be´dat ◽  
Mathieu Moreau ◽  
Olivier Simonin

This paper presents an Euler-Euler Large-Eddy Simulation (LES) approach for the numerical modeling of non isothermal dispersed turbulent two-phase flows. The proposed approach is presented and validated by a priori tests from an Euler-Lagrange database, provided using discrete particle simulation (DPS) of the particle phase coupled with direct numerical simulation (DNS) of the turbulent carrier flow, in a non isothermal particle-laden temporal jet configuration. A statistical approach, the Mesoscopic Eulerian Formalism (MEF) [Fe´vrier et al., J. Fluid Mech., 2005, vol. 533, pp. 1–46], is used to write local and instantaneous Eulerian equations for the dispersed phase and then, by spatial averaging, to derive the LES equations governing the filtered variables. In this work, the MEF approach is extended to scalar variables transported by the particles in order to develop LES for reactive turbulent dispersed two-phase flows with mass and heat turbulent transport. This approach leads to separate the instantaneous particle temperature distribution in a Mesoscopic Eulerian field, shared by all the particles, and a Random Uncorrelated distribution which may be characterized in terms of Eulerian fields of particle moments such as the uncorrelated temperature variance. In this paper, the DPS-DNS numerical database is presented, LES Eulerian equations for the dispersed phase are derived in the frame of the Mesoscopic approach and models for the unresolved subgrid and random uncorrelated terms are proposed and a priori tested using the DPS-DNS database.


2007 ◽  
Vol 23 (6) ◽  
pp. 635-643 ◽  
Author(s):  
Xuelin Tang ◽  
Fujun Wang ◽  
Yulin Wu

Author(s):  
Mohammad Rahnama ◽  
Mazyar Salmanzadeh ◽  
Goodarz Ahmadi

Particle transport and deposition in a turbulent channel flow simulated by the Large Eddy simulations (LES) were studied. Particular attention was paid to the effect of subgrid scales (SGS) turbulence fluctuation on particle motion. Finite volume method was used for finding instantaneous filtered fluid velocity fields of LES of the continuous phase in the channel. Selective structure function model was used to account for the subgrid-scale Reynolds stresses. It was shown that the LES was capable of capturing the turbulence near wall coherent eddy structures. Particle motions were investigated using a Lagrangian particle tracking approach with inclusion of the Stokes drag, lift, Brownian and gravity forces. Effects of SGS of turbulence fluctuations on deposition rate of different size particles were studied. It was shown that the inclusion of the SGS turbulence fluctuations improves the model predictions for particle deposition rate especially for small particles.


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