Particle resolved direct numerical simulation of a liquid–solid fluidized bed: Comparison with experimental data

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao. (10), respectively. In this paper, we compare the statistical quantities computed from numerical results with the experimental data obtained with 3-D trajectography and High Frequency PIV. Fluidization law predicted by the numerical simulations is in very good agreement with the experimental curve and the main features of trajectories and Lagrangian velocity signal of the particles are well reproduced by the simulations. The evolution of particle and flow velocity variances as a function of bed solid volume fraction is also well captured by the simulations. In particular, the numerical simulations predict the right level of anisotropy of the dispersed phase fluctuations and its independence of bed solid volume fraction. They also confirm the high value of the ratio between the fluid and the particle phase fluctuating kinetic energy. A quick analysis suggests that the fluid velocity fluctuations are mainly driven by fluid-particle wake interactions (pseudo-turbulence) whereas the particle velocity fluctuations derive essentially from the large scale flow motion (recirculation). Lagrangian autocorrelation function of particle fluctuating velocity exhibits large-scale oscillations, which are not observed in the corresponding experimental curves, a difference probably due to a statistical averaging effect. Evolution as a function of the bed solid volume fraction and the collision frequency based upon transverse component of particle kinetic energy correctly matches the experimental trend and is well fitted by a theoretical expression derived from Kinetic Theory of Granular Flows.

Toward Constitutive Models for Momentum, Species, and Energy Transport in Gas–Particle Flows

“…PR-DNS simulations of fluidization (9) have revealed the emergence of 1D traveling waves in small domains and bubble-like voids in larger domains. PR-DNS simulations have also successfully captured experimental data gathered in small fluidized beds (11). These observations provide validation of PR-DNS as a tool to develop constitutive models for higher (i.e., coarser) levels of fluid-solid flow modeling (12,46).…”

“…Given the multiscale nature of gas-particle flows, several different modeling and simulation approaches are being used to probe flow behavior at different scales, with simpler models being used at coarser scales (see, e.g., 6, 7). Particle-resolved direct numerical simulation (PR-DNS) seeks to resolve all scales of flow (see, e.g., 6,[8][9][10][11]. Particles are tracked in a Lagrangian fashion by solving Newton's equations, and particle-particle interaction is accounted for via a hard-or soft-sphere contact model.…”

Analysis of the effect of small amounts of liquid on gas–solid fluidization using CFD‐DEM simulations

“…Computational modeling of fluidization exists on many length scales, ranging from particle‐resolved direct numerical simulation (PR‐DNS) in which fluid and particle motion are resolved fully without the need for closure relationships, to models capable of simulating industrial‐scale systems. PR‐DNS suffers from only being able to simulate thousands of particles unless tens of thousands of processors are used and thus not being able to capture many of the phenomena observed in larger beds.…”

Accurate estimate of drag forces using particle-resolved direct numerical simulations

“…The penalty method has been validated on numerous analytical and experimental reference solutions in [9,10,34,39,[41][42][43].…”