International Journal of Multiphase Flow, Vol.79, 144-158, 2016
Particle-laden flows forced by the disperse phase: Comparison between Lagrangian and Eulerian simulations
The goal of the present work is to assess the ability of Eulerian moment methods to reproduce the physics of two-way coupled particle-laden turbulent flow systems. Previous investigations have been focused on effects such as preferential concentration, and turbulence modulation, but in regimes in which turbulence is sustained by an imposed external forcing. We show that in such regimes, Eulerian methods need resolutions finer than nominal Kolmogorov scale in order to capture statistics of particle segregation, but gas and disperse phase velocity variances can be captured with resolutions comparable to the Kolmogorov length. The work is then extended to address the question whether Eulerian methods are suitable in scenarios in which the continuum field of interest (temperature or momentum) is itself primarily driven by particles. To this end we have extended our analysis to the problem of turbulence driven by heated particles (Zamansky et al. PoF 2014) and have assessed capabilities of Eulerian methods in capturing particle segregation, as well as statistics of the temperature and velocity fields. Separate investigations are developed for cases with and without buoyancy driven turbulence. For each case corresponding Lagrangian calculations are developed and convergence of statistics with respect to the number of particles is established. Then the statistically converged Lagrangian and Eulerian results are compared. Results show that accurate capture of segregation by the Eulerian methods always requires resolutions much higher than the nominal Kolmogorov scale. In scenarios for which a continuum phase is forced by particles, results from Eulerian methods show some sensitivity of predicted continuum statistics to the mesh resolution. This sensitivity was found to be largest for the case of a temperature field forced by hot particles, but without presence of buoyancy. In this case a Eulerian method with nominal Kolmogorov resolution was found to be insufficient for capture of temperature statistics. When additional coupling between particles and continuum phase is introduced by including the buoyancy effects, this sensitivity is suppressed in the temperature field, but some sensitivity to the Eulerian mesh resolution were detected in the momentum fields. (C) 2015 Elsevier Ltd. All rights reserved.