Turbulence Induced Cloud Voids: Observation and Interpretation

Karpińska, Katarzyna; Bodenschatz, Jonathan F. E.; Malinowski, Szymon P.; Nowak, Jakub; Risius, Steffen; Schmeissner, T.; Shaw, R. Anthony; Siebert, Holger; Xi, Heng-Dong; Xu, Hui; Bodenschatz, Eberhard

doi:10.5194/acp-2018-1049

Cited by 2 publications

(3 citation statements)

References 17 publications

(28 reference statements)

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“…This result could be connected to "cloud voids" reported by Karpińska et al [46]. They observed many void regions with the diameter of up to 12 cm during mountain observations and explained that the phenomenon is caused by the inertial motion of cloud particles.…”

Section: Stokes Number Dependencesupporting

confidence: 55%

Scale-dependent statistics of inertial particle distribution in high Reynolds number turbulence

Matsuda,

Schneider,

Yoshimatsu

2020

Preprint

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Multiscale statistical analyses of inertial particle distributions are presented to investigate the statistical signature of clustering and void regions in particle-laden incompressible isotropic turbulence. Three-dimensional direct numerical simulations of homogeneous isotropic turbulence at high Reynolds number (Re λ 200) with up to 10 9 inertial particles are performed for Stokes numbers ranging from 0.05 to 5.0. Orthogonal wavelet analysis is then applied to the computed particle number density fields. Scale-dependent skewness and flatness values of the particle number density distributions are calculated and the influence of Reynolds number Re λ and Stokes number St is assessed. For St ∼ 1.0, both the scale-dependent skewness and flatness values become larger as the scale decreases, suggesting intermittent clustering at small scales. For St ≤ 0.2, the flatness at intermediate scales, i.e. for scales larger than the Kolmogorov scale and smaller than the integral scale of the flow, increases as St increases, and the skewness exhibits negative values at the intermediate scales. The negative values of the skewness are attributed to void regions. These results indicate that void regions at the intermediate sales are pronounced and intermittently distributed for such small Stokes numbers. As Re λ increases, the flatness increases slightly. For Re λ ≥ 328, the skewness shows negative values at large scales, suggesting that void regions are pronounced at large scales, while clusters are pronounced at small scales.

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Section: Stokes Number Dependencesupporting

confidence: 55%

Scale-dependent statistics of inertial particle distribution in high Reynolds number turbulence

Matsuda,

Schneider,

Yoshimatsu

2020

Preprint

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“…Comparison of the two described cases becomes straightforward when conducted on the basis of the movies in the database (Karpinska et al, 2018). In the movie "ms01" between 13s and 22s there are two cloud void appearances.…”

Section: Experimental Evidencementioning

confidence: 99%

“…Figure 6 presents a 3D picture (panels a and b) with a 2D cross-section (c and d) at the last, quasi stationary stage of simulations 1) and 2). In the database (Karpinska et al, 2018) one may find animations from the simulations both in 2D and 3D. Animations "ms03" and "ms04" correspond to set 1), "ms05" and "ms06" to set 2), "ms07" and "ms08" to set 3).…”

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confidence: 99%

Final response to revievers comments

Karpińska¹

2019

Preprint

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The phenomenon of "cloud voids", i.e., elongated volumes inside a cloud that are devoid of droplets, was observed with laser sheet photography in clouds at a mountain-top station. Two experimental cases, similar in turbulence conditions yet with diverse droplet size distributions and cloud void prevalence, are reported. A theoretical explanation is proposed based on the study of heavy inertial sedimenting particles inside a Burgers vortex. A general conclusion regarding void appearance is drawn from theoretical analysis. Numerical simulations of polydisperse droplet motion with realistic vortex parameters and Mie scattering visual effects accounted for can explain the presence of voids with sizes similar to that of the observed ones. Preferential concentration and sorting effects in a vortex tube are discussed for reasonable cloud conditions. Copyright statement. TEXT 1 Introduction The dynamics of heavy inertial particles in turbulent flow is a universal problem that appears in astrophysics, oceanography, engineering and atmospheric sciences. In particular, in cloud physics, deeper understanding of the interaction between atmospheric turbulence and cloud droplets is seen as a potential answer to many important questions (Bodenschatz et al. (2010)). Over the years, there has been considerable speculation about the possible role of coherent, long-lived vortex structures in cloud turbulence and microphysical processes, including both condensation growth and collision-coalescence growth (see Tennekes

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Turbulence Induced Cloud Voids: Observation and Interpretation

Cited by 2 publications

References 17 publications

Scale-dependent statistics of inertial particle distribution in high Reynolds number turbulence

Scale-dependent statistics of inertial particle distribution in high Reynolds number turbulence

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