Inertial Clustering of Particles in High-Reynolds-Number Turbulence

Saw, Ewe-Wei; Shaw, Raymond A.; Ayyalasomayajula, Sathyanarayana; Chuang, P. Y.; Gylfason, Ármann

doi:10.1103/physrevlett.100.214501

Cited by 143 publications

(136 citation statements)

References 35 publications

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“…Right panel: The two scale ratios P 1 and P 2 defined in Equations (2) and (3) as a function of a 2 /a 1 with a 1 = 30 µm. Saw et al (2008) have recently obtained convincing experimental evidence of droplet-pair clustering in high-Reynolds-number turbulence, with results in quantitative agreement with published theoretical and numerical results. The above formulation is applicable to aerodynamically interacting droplets in a turbulent background flow, showing that the total enhancement factor η T of the collision rate is a product of the enhancement of the geometric collision, η G , and the enhancement of the collision efficiency, η E .…”

Section: Hybrid Simulation Approachsupporting

confidence: 73%

The role of air turbulence in warm rain initiation

Wang

Grabowski

2009

Atmospheric Science Letters

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Quantitative parameterization of turbulent collision of cloud droplets represents a major unsolved problem in cloud physics. Here a hybrid direct simulation tool is used specifically to quantify the turbulent enhancement of the gravitational collision-coalescence. Simulation results show that air turbulence can enhance the collision kernel by an average factor of about 2, and the observed trends are supported by scaling arguments. An impact study using the most realistic collection kernel suggests that cloud turbulence can significantly reduce the time for warm rain initiation. Areas for further development of the hybrid simulation and the impact study are indicated.

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Section: Hybrid Simulation Approachsupporting

confidence: 73%

The role of air turbulence in warm rain initiation

Wang

Grabowski

2009

Atmospheric Science Letters

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“…They too find that the clustering is strongest for scales less than 10η and for St ∼ 1, although in these and in the other experiments reported here there is significant clustering at lower St. The results of Saw et al (2008) show scale separation of inertial-range clustering due to mixing and dissipation-range clustering due to inertia. The behaviour of bidisperse and polydisperse RDFs were found to be in good agreement with DNS (Saw, pers.…”

Section: Laboratory Experimentsmentioning

confidence: 53%

“…All of these box turbulence measurements were made for R λ of the order of a few hundred. Saw et al (2008) determined the 1-D RDF in a wind tunnel with water sprays for an St range from 0.3 to 1.5 at R λ ≈ 500. They too find that the clustering is strongest for scales less than 10η and for St ∼ 1, although in these and in the other experiments reported here there is significant clustering at lower St.…”

Section: Laboratory Experimentsmentioning

confidence: 99%

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

243

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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“…Beyond practical applications, it is rather clear that these problems also exert an appeal on researchers and scientists as a consequence of the complexity of the possible stages of evolution, of the non-linear behavior and because these organized particle structures are aesthetically and philosophically pleasing as well as irresistible to theoretical physicists (Balkovsky et al, 2001;Saw et al, 2008;Di Carlo et al, 2009). Moreover, the fact that strikingly well-ordered and similar phenomena are found also in other systems (not just physical, but also chemical and biological systems; see, e.g., Carotenuto et al, 2002;Lappa, 2003b and2011), indicates that these subjects really stand at the intersection of many scientific branches (which make them a multi-domain field of investigations and a truly interdisciplinary science).…”

Section: Resultsmentioning

confidence: 99%

“…As additional examples, Maxey et al (1997) and Saw et al (2008) reported numerical and experimental evidence, respectively, of spatial clustering of dense particles in high-Re homogenous, isotropic turbulence. The dissipation-scale clustering was found to become stronger for increasing values of the Stokes number.…”

Section: Introductionmentioning

confidence: 99%

On the variety of particle accumulation structures under the effect of g-jitters

Lappa¹

2013

J. Fluid Mech.

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The present analysis extends the author's earlier work (Lappa, Phys. Fluids 25(1) and Chaos 23(1)) on the properties of patterns formed by the spontaneous accumulation and ordering of solid particles in certain types of flow (with a toroidal structure and a traveling wave propagating in the azimuthal direction) by considering the potential impact of "vibrations" (gjitters) on such dynamics. It is shown that a kaleidoscope of possible variants exist whose nature and variety calls for a concerted analysis using the tools of computational fluid-dynamics in synergy with dimensional arguments and existing theories on the effect of periodic accelerations on fluid systems.A possible categorization of the observed phenomena is introduced according to the type and scale of "defects" displayed by the emerging particle aggregates with respect to unperturbed (vibrationless) conditions. It is shown that the resulting degree of "turbulence" depends essentially on the direction (), amplitude () and frequency () of the applied inertial disturbance. A range of amplitudes and frequencies exist where the formation of recognizable particle structures is prevented. A quantitative map (in the - plane) for their occurrence is derived with the express intent of supporting the optimization of future experiments to be performed in space.

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Inertial Clustering of Particles in High-Reynolds-Number Turbulence

Cited by 143 publications

References 35 publications

The role of air turbulence in warm rain initiation

The role of air turbulence in warm rain initiation

Droplet growth in warm turbulent clouds

On the variety of particle accumulation structures under the effect of g-jitters

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