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Understanding the two-way interactions between finite-size solid particles and a wall-bounded turbulent flow is crucial in a variety of natural and engineering applications. Previous experimental measurements and particle-resolved direct numerical simulations revealed some interesting phenomena related to particle distribution and turbulence modulation, but their in-depth analyses are largely missing. In this study, turbulent channel flows laden with neutrally buoyant finite-size spherical particles are simulated using the lattice Boltzmann method. Two particle sizes are considered, with diameters equal to 14.45 and 28.9 wall units. To understand the roles played by the particle rotation, two additional simulations with the same particle sizes but no particle rotation are also presented for comparison. Particles of both sizes are found to form clusters. Under the Stokes lubrication corrections, small particles are found to have a stronger preference to form clusters, and their clusters orientate more in the streamwise direction. As a result, small particles reduce the mean flow velocity less than large particles. Particles are also found to result in a more homogeneous distribution of turbulent kinetic energy (TKE) in the wall-normal direction, as well as a more isotropic distribution of TKE among different spatial directions. To understand these turbulence modulation phenomena, we analyse in detail the total and component-wise volume-averaged budget equations of TKE with the simulation data. This budget analysis reveals several mechanisms through which the particles modulate local and global TKE in the particle-laden turbulent channel flow.
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Classical Nucleation Theory and Tolman Equation in Cluster Thermodynamics: How Small Can They Truly Apply?
Classical nucleation theory and the Tolman equation are two fundamental theories in cluster thermodynamics. Despite their long-standing existence, the applicability of these theories remains questionable. Direct experimental validation is challenging due to the small size of the clusters involved. While theoretical approaches are often used as alternatives, the findings are frequently controversial. In this work, free energy calculations were performed across an unprecedentedly large size range using sophisticated techniques, including aggregation-volume-bias Monte Carlo, for two systems: Lennard-Jones and TIP4P/2005 water. The availability of bulk-phase properties for an infinitely large system (i.e., ) facilitates a direct comparison to these two theories. The simulation results provide strong support for the applicability of these theories to large clusters, down to those containing a few hundred particles. However, these theories break down for small clusters.
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- Award ID(s):
- 2413803
- PAR ID:
- 10618703
- Publisher / Repository:
- Journal of Physical Chemistry
- Date Published:
- Journal Name:
- The Journal of Physical Chemistry A
- Volume:
- 129
- Issue:
- 27
- ISSN:
- 1089-5639
- Page Range / eLocation ID:
- 6018 to 6023
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acs.jpca.5c02843
