Experimental and numerical investigation of inertial particle clustering in isotropic turbulence

Salazar, Juan P. L. C.; Jong, Jeremy de; Cao, Lujie; Woodward, Scott H.; Meng, Hui; Collins, Lance R.

doi:10.1017/s0022112008000372

Cited by 163 publications

(141 citation statements)

References 38 publications

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“…Yang and Shy (2005) also show that, for 0.3 ≤ St ≤ 1.9, clustering is greatest for St ∼ 1. Salazar et al (2008) andde Jong et al (2010) study (experimentally) the full 3-D RDF for 0.21 ≤ St ≤ 0.6 and the former also provide excellent confirmation of their clustering measurements at the small scales using DNS. All of these box turbulence measurements were made for R λ of the order of a few hundred.…”

Section: Laboratory Experimentsmentioning

confidence: 55%

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

245

281

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In this survey we consider the impact of turbulence on cloud formation from the cloud scale to the droplet scale. We assess progress in understanding the effect of turbulence on the condensational and collisional growth of droplets and the effect of entrainment and mixing on the droplet spectrum. The increasing power of computers and better experimental and observational techniques allow for a much more detailed study of these processes than was hitherto possible. However, much of the research necessarily remains idealized and we argue that it is those studies which include such fundamental characteristics of clouds as droplet sedimentation and latent heating that are most relevant to clouds. Nevertheless, the large body of research over the last decade is beginning to allow tentative conclusions to be made. For example, it is unlikely that small-scale turbulent eddies (i.e. not the energy-containing eddies) alone are responsible for broadening the droplet size spectrum during the initial stage of droplet growth due to condensation. It is likely, though, that small-scale turbulence plays a significant role in the growth of droplets through collisions and coalescence. Moreover, it has been possible through detailed numerical simulations to assess the relative importance of different processes to the turbulent collision kernel and how this varies in the parameter space that is important to clouds. The focus of research on the role of turbulence in condensational and collisional growth has tended to ignore the effect of entrainment and mixing and it is arguable that they play at least as important a role in the evolution of the droplet spectrum. We consider the role of turbulence in the mixing of dry and cloudy air, methods of quantifying this mixing and the effect that it has on the droplet spectrum. Copyright

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Section: Laboratory Experimentsmentioning

confidence: 55%

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

245

281

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“…Larval Stokes numbers were generally St<<1, reaching only St≈0.01 at the threshold dissipation rate and St≈0.1 at the highest dissipation rate (Fig.7B). These low Stokes numbers indicate that larvae had short response times and would be unlikely to form clusters or experience a downward bias in turbulent transport (Salazar et al, 2008).…”

Section: Scales Of Larvae and Turbulencementioning

confidence: 99%

Active downward propulsion by oyster larvae in turbulence

Fuchs

Hunter

Schmitt

et al. 2012

Journal of Experimental Biology

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SUMMARYOyster larvae (Crassostrea virginica) could enhance their settlement success by moving toward the seafloor in the strong turbulence associated with coastal habitats. We characterized the behavior of individual oyster larvae in grid-generated turbulence by measuring larval velocities and flow velocities simultaneously using infrared particle image velocimetry. We estimated larval behavioral velocities and propulsive forces as functions of the kinetic energy dissipation rate ε, strain rate γ, vorticity ξ and acceleration α. In calm water most larvae had near-zero vertical velocities despite propelling themselves upward (swimming). In stronger turbulence all larvae used more propulsive force, but relative to the larval axis, larvae propelled themselves downward (diving) instead of upward more frequently and more forcefully. Vertical velocity magnitudes of both swimmers and divers increased with turbulence, but the swimming velocity leveled off as larvae were rotated away from their stable, velum-up orientation in strong turbulence. Diving speeds rose steadily with turbulence intensity to several times the terminal fall velocity in still water. Rapid dives may require a switch from ciliary swimming to another propulsive mode such as flapping the velum, which would become energetically efficient at the intermediate Reynolds numbers attained by larvae in strong turbulence. We expected larvae to respond to spatial or temporal velocity gradients, but although the diving frequency changed abruptly at a threshold acceleration, the variation in propulsive force and behavioral velocity was best explained by the dissipation rate. Downward propulsion could enhance oyster larval settlement by raising the probability of larval contact with oyster reef patches.

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“…The particles assembled in these regions make clusters with higher particle number densities than the mean number density. This effect, known as inertial clustering, has been investigated in a number of analytical, numerical, and experimental studies [15][16][17][18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Mechanism of unconfined dust explosions: Turbulent clustering and radiation-induced ignition

2017

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It is known that unconfined dust explosions typically start off with a relatively weak primary flame followed by a severe secondary explosion. We show that clustering of dust particles in a temperature stratified turbulent flow ahead of the primary flame may give rise to a significant increase in the radiation penetration length. These particle clusters, even far ahead of the flame, are sufficiently exposed and heated by the radiation from the flame to become ignition kernels capable to ignite a large volume of fuel-air mixtures. This efficiently increases the total flame surface area and the effective combustion speed, defined as the rate of reactant consumption of a given volume. We show that this mechanism explains the high rate of combustion and overpressures required to account for the observed level of damage in unconfined dust explosions, e.g., at the 2005 Buncefield vapor-cloud explosion. The effect of the strong increase of radiation transparency due to turbulent clustering of particles goes beyond the state of the art of the application to dust explosions and has many implications in atmospheric physics and astrophysics.

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Experimental and numerical investigation of inertial particle clustering in isotropic turbulence

Cited by 163 publications

References 38 publications

Droplet growth in warm turbulent clouds

Droplet growth in warm turbulent clouds

Active downward propulsion by oyster larvae in turbulence

Mechanism of unconfined dust explosions: Turbulent clustering and radiation-induced ignition

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