Two- or three-dimensional simulations of turbulent gas–solid flows applied to fluidization

Comparison between two-fluid model simulations and particle image analysis & velocimetry (PIV) results for a two-dimensional gas–solid fluidized bed

“…This is perhaps due to its compromise between computational cost, level of detail provided, and potential of applicability. As a conse quence, there is an increasing need of verification and validation of the closure models utilised in the two fluid simulation of gas fluidized beds in different operative conditions and applications (see, for instance, Peirano et al, 2001;McKeen and Pugsley, 2003;Patil et al, 2005;Taghipour et al, 2005;Li et al, 2009). However, as some authors have pointed out (Grace and Taghipour, 2004), this verification and validation should be interpreted and extra polated with caution due to the complex nature of fluidized beds.…”

Gas Fluidisation of Nano-particle Assemblies: Modified Geldart classification to account for multiple-scale fluidisation of agglomerates and clusters

“…10 Proposed modification of Geldart's classification to incorporate nano-particle fluidization regimes (dp=particle/agglomerate size and (ρ p-ρ g ) is the immersed solids density) ometry on the observed transitions from particulate to aggregative states of fluidisation both within the agglomerates as well as with in the cavity space between the "ef fective" agglomerates in the bed. The other very recent literature cited above in 3-D beds 24) suggests that the transitions from particulate fluidisation to aggregative and/ or bubbling regime is markedly different in 2-D and 3-D geometries. All of these phenomena could be fitted into the Geldart classification above by a further systematic study of the dynamics of the agglomerate/cluster growth and decay processes in 2-D and 3-D fluidised beds.…”

Comprehensive Approaches to Multiphase Flows in Geophysics - Application to nonisothermal, nonhomogenous, unsteady, large-scale, turbulent dusty clouds I. Hydrodynamic and Thermodynamic RANS and LES Models

“…Although RANS approaches have received considerable attention these past decades, these models have led to disappointing results with computer costs being higher and higher as the RANS models become more and more sophisticated [e.g., Sagaut et al, 1997;Lakehal 2002]. RANS approaches have been quite extensively developed for multiphase flows [e.g., Besnard et al, 1987Besnard et al, , 1992Simonin 1996;Kashiwa and Vanderheyden 2000;Peirano et al, 2001]. However, to the best of our knowledge, these multiphase models have never been applied to large-scale geophysical multiphase flows.…”

“…where C d and Re s are the mean drag coefficient and the mean particle Reynolds number [Peirano et al, 2001]; d s is the grain diameter; and µ g is the molecular viscosity of the carrier phase. The drift velocity accounts for the dispersion effect from the particle transport by the fluid turbulence; hence, it represents the correlation between turbulence in the gas phase and the spatial distribution of the particles.…”