Creation of Prompt and Thin-Sheet Splashing by Varying Surface Roughness or Increasing Air Pressure

Latka, Andrzej; Strandburg‐Peshkin, Ariana; Driscoll, Michelle; Stevens, Cacey; Nagel, Sidney R.

doi:10.1103/physrevlett.109.054501

Cited by 125 publications

(146 citation statements)

References 24 publications

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“…Interestingly, aerosol generation was observed for surface roughness (RMS) ranging from 1 to 10 mm. This range is slightly higher than the air film thickness (1 mm) formed on solid surfaces during impact 38,53 . From this information we can speculate as to why aerosol is not generated on highly roughened surfaces.…”

Section: Resultsmentioning

confidence: 88%

Aerosol generation by raindrop impact on soil

2015

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Aerosols are investigated because of their significant impact on the environment and human health. To date, windblown dust and sea salt from sea spray through bursting bubbles have been considered the chief mechanisms of environmental aerosol dispersion. Here we investigate aerosol generation from droplets hitting wettable porous surfaces including various classifications of soil. We demonstrate that droplets can release aerosols when they influence porous surfaces, and these aerosols can deliver elements of the porous medium to the environment. Experiments on various porous media including soil and engineering materials reveal that knowledge of the surface properties and impact conditions can be used to predict when frenzied aerosol generation will occur. This study highlights new phenomena associated with droplets on porous media that could have implications for the investigation of aerosol generation in the environment.

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Section: Resultsmentioning

confidence: 88%

Aerosol generation by raindrop impact on soil

2015

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“…This includes the effects of reduced air pressure, Xu et al (2005), or surface roughness, Latka et al (2012). For example, for our drops of D = 2.6 mm, impacting at V = 2.5 m/s, suggest that the air film can stay intact and the drop skate on it, if the surface roughness is smaller than 10 nm.…”

Section: Discussionmentioning

confidence: 99%

Time-resolved imaging of a compressible air disc under a drop impacting on a solid surface

Thoroddsen

2015

J. Fluid Mech.

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When a drop impacts on a solid surface, its rapid deceleration is cushioned by a thin layer of air, which leads to the entrapment of a bubble under its center. For large impact velocities the lubrication pressure in this air layer becomes large enough to compress the air. Herein we use highspeed interferometry, with 200 ns time-resolution, to directly observe the thickness evolution of the air-layer during the entire bubble entrapment process. The initial disc radius and thickness shows excellent agreement with available theoretical models, based on adiabatic compression. For the largest impact velocities the air is compressed by as much as a factor of 14. Immediately following the contact, the air disc shows rapid vertical expansion. The radial speed of the surface minima just before contact, can reach 50 times the impact velocity of the drop.

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“…We experimentally verify that the resulting, particle-based Weber number gives a reliable, particle size and density dependent splash onset criterion. We further show that the same argument also explains why in bimodal systems smaller particles are more likely to escape than larger ones.Splashing of liquid droplets upon impact on a solid surface has been investigated for over a century [1][2][3][4][5][6][7][8][9][10][11]. More recently, there has also been a growing interest in what happens to the spreading and splashing if particles are added to the liquid [12][13][14].…”

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confidence: 99%

Splashing Onset in Dense Suspension Droplets

Peters

Jaeger

2013

Phys. Rev. Lett.

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We investigate the impact of droplets of dense suspensions onto a solid substrate. We show that a global hydrodynamic balance is unable to predict the splash onset and propose to replace it by an energy balance at the level of the particles in the suspension. We experimentally verify that the resulting, particle-based Weber number gives a reliable, particle size and density dependent splash onset criterion. We further show that the same argument also explains why in bimodal systems smaller particles are more likely to escape than larger ones.Splashing of liquid droplets upon impact on a solid surface has been investigated for over a century [1][2][3][4][5][6][7][8][9][10][11]. More recently, there has also been a growing interest in what happens to the spreading and splashing if particles are added to the liquid [12][13][14]. On micron scales, ZrO 2 suspensions have been used in studies aiming to optimize ink-jet printing applications [15][16][17][18][19], and on truly macroscopic scales there has been the development of 3D printers that dispense cement slurry [20,21]. In all of these situations, an important concern is to prevent splashing, and particles from escaping, when droplets hit a surface. However, the question of when and why particles are ejected has remained unsettled, and existing experimental studies mostly focus on dilute suspensions.Current models for suspension drop impact associate the onset of splashing with the condition that K = Weexceeds a critical value K 0 , which has been the traditional criterion for pure liquid splashing on dry surfaces at atmospheric pressure in a regime independent of surface roughness [4,22,23]. Here the Weber and Reynolds numbers are defined as We d = ρ l r d U 2 /σ and Re d = ρ l r d U/µ, with r d the droplet radius, U the droplet impact velocity, and ρ l , σ and µ the liquid density, surface tension and dynamic viscosity, respectively.In these models, the addition of particles has been captured by replacing µ with an effective viscosity µ e that increases with packing fraction [12,[24][25][26][27][28]. This predicts that a droplet of a pure liquid that would splash under certain conditions should not splash after adding enough particles. To our knowledge, there exists no systematic study that confirms this prediction. In fact, Nicolas observed [12] that adding particles, instead, lowered the splashing threshold K 0 .To investigate the influence of added particles, we depart from the dilute limit described above, and instead focus here on the limit of dense granular suspensions with volume packing fractions φ = 0.62 ± 0.03, where the discrepancy with the above droplet-scale splash onset criterion is most pronounced.In pure liquid droplets, the size of the ejecta depends on either the destabilization of a thin liquid sheet [5,[29][30][31][32][33][34] or, in the case of prompt splashing, on an instability at the moving contact line [5,10,35]. At splash onset in a suspension, on the other hand, the ejecta are the solid particles (see Fig. 1), which implies a built-in...

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Creation of Prompt and Thin-Sheet Splashing by Varying Surface Roughness or Increasing Air Pressure

Cited by 125 publications

References 24 publications

Aerosol generation by raindrop impact on soil

Aerosol generation by raindrop impact on soil

Time-resolved imaging of a compressible air disc under a drop impacting on a solid surface

Splashing Onset in Dense Suspension Droplets

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