The Physical Products of a Splashing Water Drop

Stow, C. D.; Stainer, R. D.

doi:10.2151/jmsj1965.55.5_518

Cited by 104 publications

(58 citation statements)

References 11 publications

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“…The correlations are in good agreement in comparison to experimental data [15] [24]. Ejection angles of the secondary droplets are typically in the range of α 10 AE to α 15 AE relative to the wall whereas initial velocities are about 60% of the impact value.…”

Section: Wall Interactionsupporting

confidence: 75%

Predictions of Transient Fuel Spray Phenomena in the Intake Port of a Si-Engine

Burger¹,

Schmehl²,

Gorse³

et al. 2002

SAE Technical Paper Series

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The present study addresses the numerical prediction of the two-phase flow in the intake port of a SI-engine. Particular emphasis is put on transient phenomena, as well as secondary effects, such as droplet breakup and droplet wall interaction. These phenomena have a significant influence on the fuel air mixture characteristics and cannot be neglected in the numerical prediction. The numerical methodology, presented in this paper, is based on a 3D body-fitted Finite Volume discretization of the gas flow field and a Lagrangian particle tracking algorithm of the disperse fuel phase. The Unsteady Reynolds Averaged Navier-Stokes equations (URANS) are solved by a time-implicit three level scheme. In the Lagrangian particle tracking algorithm, the spray is modeled by superposition of a large number of droplet trajectories. Two advanced numerically effective models are presented for the prediction of droplet breakup and droplet wall interaction. Special emphasis is put on the correct reproduction of the droplet statistics. In the present study the fuel injection and spray preparation process within the intake port of a SI-engine is investigated. Spray preparation is dominated by atomization processes like droplet breakup and wall interaction which predominantly take place at the valve seat. In order to find the principal characteristics of fuel preparation in a SI-engine, a parametric study has been carried out focusing on the influence of the gap sizes of the intake valve which strongly affects the complete fuel preparation process. The study is concluded by an analysis of qualitative and quantitative results of the predicted flow field.

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Section: Wall Interactionsupporting

confidence: 75%

Predictions of Transient Fuel Spray Phenomena in the Intake Port of a Si-Engine

Burger¹,

Schmehl²,

Gorse³

et al. 2002

SAE Technical Paper Series

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“…The impact of a liquid drop onto a rigid surface results in a rapid sequence of events ending, in the inertial limit, in spreading (Eggers et al 2010) or splashing (Stow & Hadfield 1981), interface tearing (Villermaux & Bossa 2011) and ultimate fragmentation (Stow & Stainer 1977). A large number of studies have investigated the many facets of drop impact, with a special attention to the description of its late stages (Rein 1993;Yarin & Weiss 1995).…”

Section: Introductionmentioning

confidence: 99%

Drop impact on a solid surface: short-time self-similarity

2016

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The early stages of drop impact onto a solid surface are considered. Detailed numerical simulations and detailed asymptotic analysis of the process reveal a self-similar structure both for the velocity field and the pressure field. The latter is shown to exhibit a maximum not near the impact point, but rather at the contact line. The motion of the contact line is furthermore shown to exhibit a 'tank treading' motion. These observations are apprehended at the light of a variant of Wagner theory for liquid impact. This framework offers a simple analogy where the fluid motion within the impacting drop may be viewed as the flow induced by a flat rising expanding disk. The theoretical predictions are found to be in very close agreement both qualitatively and quantitatively with the numerical observations for about three decades in time. Interestingly the inviscid self-similar impact pressure and velocities are shown to depend solely on the self-similar variables (r/ √ t, z/ √ t). The structure of the boundary layer developing along the wet substrate is investigated as well, and is proven to be formally analogous to that of the boundary layer growing in the trail of a shockwave. Interestingly, the boundary layer structure only depends on the impact self-similar variables. This allows to construct a seamless uniform analytical solution encompassing both impact and viscous effects. The depiction of the different dynamical fields enables to quantitatively predict observables of interest, such as the evolution of the integral viscous shearing force and of the net normal force. IntroductionThe impact of a liquid drop onto a rigid surface results in a rapid sequence of events ending, in the inertial limit, in spreading (Eggers et al. 2010) or splashing (Stow & Hadfield 1981), interface tearing (Villermaux & Bossa 2011) and ultimate fragmentation (Stow & Stainer 1977). A large number of studies have investigated the many facets of drop impact, with a special attention to the description of its late stages (Rein 1993;Yarin & Weiss 1995). The literature on the early stages of impact is however scarce in comparison. Detailed experimental data depicting the instants following impact can nonetheless be found in the work of Rioboo et al. (2002), that evidenced a "kinematic phase" where the drop merely resembles a truncated sphere and spreads as the squareroot of time. This phase precedes the apparition of the liquid lamella.Probably one of the first depiction of the very first instants of drop impact dates back to Engel (1955). With the help of high-speed cinematography, Engel captured the chronology of events triggered by drop impact. He noted in particular the unvarying shape of the drop apex during the earliest moments of impact, which might be surprising due to the incompressible character of the liquid. Engel put forward the possible roles of inertia, viscosity or surface tension to explain this observation. Actually, the physical mechanism underpinning this behaviour is best illustrated with Figure 1a. There, the numerically...

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“…The relationship is superior to that proposed by Stow and Stainer (1977) in that it provides the correct functional relationship between R and VT, and correctly predicts values of N observed by Stow and Stainer. For drops impacting at their terminal velocity, the effect of the roughness of the target is believed to be crucial in predicting the occurrence of a splash only if drops possess radii in the range 0.5-0.8mm; for smaller drops no splash is likely, even on a very rough surface, and larger drops will splash on a perfectly smooth surface.…”

Section: Introductionmentioning

confidence: 46%

“…In particular, she noted that the impacts she observed with a polished metal surface produced no splash products; Levin and Hobbs (1971) in their study of the hydrodynamics and charge separation effects associated with drop impacts, avoided the use of smooth targets for this reason. Stow and Stainer (1977), on the other hand, used a direct method of droplet collection to determine the numbers and sizes of the splash products and they were able to establish certain empirical relationships between these data and the initial conditions of the splash as determined by the impact velocity, drop size, surface tension, and the radius of curvature and the roughness of their metal targets. For a flat target, described as being "medium rough", they found that the number of droplets N ejected during a splash could be estimated by an expression of the form N=3.4 R3V2-63 provided the radius of the impacting drop R(mm) and the velocity of impact V(ms-1) are known.…”

Section: Introductionmentioning

confidence: 99%

An Investigation of the Condition for Splashing of Water Drops on Solid, Dry Surfaces

Stow¹,

Hadfield²

1980

Journal of the Meteorological Society of Japan

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Flash photography was used to examine the impact of water drops with flat, solid surfaces in order to determine the influence of drop size R and surface roughness parameter Ra upon the critical impact velocity VT above which splashing occurs. The existence of a critical impact velocity may be inferred from the literature but has not been proven prior to these experiments.It is shown that for a given surface roughness the product ST= RVT1.69 remains constant for the range R=0.70-2.25mm, suggesting that the condition for splashing is determined uniquely by the Reynolds Number and the Weber Number.The critical impact velocity VT is a decreasing function of Ra (the mean absolute deviation of surface contour from the mean surface level) and the variation of VT with Ra is of the order 3ms-1 *m-1 for Ra<1 *m; for surfaces of Ra> 1 *m, the corresponding variation is of the order 0.05ms-1 *m-1.The data obtained here suggest that the number of drops produced per collision N may be predicted by the relationship N=k[R3V2-R182ST1.18] where k is an experimentally determined constant and V is the actual impact velocity of the drop. The relationship is superior to that proposed by Stow and Stainer (1977) in that it provides the correct functional relationship between R and VT, and correctly predicts values of N observed by Stow and Stainer. For drops impacting at their terminal velocity, the effect of the roughness of the target is believed to be crucial in predicting the occurrence of a splash only if drops possess radii in the range 0.5-0.8mm; for smaller drops no splash is likely, even on a very rough surface, and larger drops will splash on a perfectly smooth surface. Although of, perhaps, secondary importance, it was also noted that VT is higher for the more prolate drops of any given mass; the effect of drop eccentricity on the splash process has not been previously documented. These data may facilitate computations of those microphysical processes within clouds which involve collisions between ice particles and water drops and which may lead to the production of secondary drops.

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The Physical Products of a Splashing Water Drop

Cited by 104 publications

References 11 publications

Predictions of Transient Fuel Spray Phenomena in the Intake Port of a Si-Engine

Predictions of Transient Fuel Spray Phenomena in the Intake Port of a Si-Engine

Drop impact on a solid surface: short-time self-similarity

An Investigation of the Condition for Splashing of Water Drops on Solid, Dry Surfaces

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