Normal droplet impact on horizontal moving films: an investigation of impact behaviour and regimes

Alghoul, Samah K.; Eastwick, Carol; Hann, David

doi:10.1007/s00348-010-0991-0

Cited by 55 publications

(29 citation statements)

References 25 publications

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“…When the film is deeper, the droplet liquid does not contribute to the crown. This correlates with observations by (Alghoul et al 2011) that crown formation happens at lower film thicknesses and that at higher film thicknesses the major outcome is jetting behaviour until the impact parameters are large enough, then a crown can form.…”

Section: Evolution Of the Droplet Liquidsupporting

confidence: 75%

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A study of droplet impact on static films using the BB-LIF technique

et al. 2016

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Section: Evolution Of the Droplet Liquidsupporting

confidence: 75%

“…Cossali et al (1997) and Okawa et al (2006) have used an impact parameter K = We OH −0.4 that can be used to predict the impact outcome. It was noted by (Alghoul et al 2011) that there was a change in behaviour of the droplet impact around h* = 1. Below this value there was crown formation and crown break-up.…”

Section: Resultsmentioning

confidence: 99%

A study of droplet impact on static films using the BB-LIF technique

et al. 2016

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“…This is important, as thick films tend towards jetting behaviours [1,9,15], whilst thin films tend towards crowning behaviours [4,10,[16][17][18].…”

Section: Controlling Dimensionless Parametersmentioning

confidence: 99%

“…Alghoul et al [1] investigated normal droplet impingement on sub-critical moving films. It was observed that the craters formed after impact were not initially symmetrical but that they became more symmetrical with time, eventually forming a cone with a sharp point before collapsing inwards.…”

Section: Impingement Upon Moving Filmsmentioning

confidence: 99%

“…When it comes to characterising the outcome from a droplet-film impact event it transpires that although there is a significant body of experimental literature covering droplet impacts onto static films there is very little published for impacts onto moving films. A study by Alghoul et al [1] for droplets impinging almost normally onto a subcritical film (film with Froude number less than 1) showed that the impingement outcomes and crater morphologies were subtly changed/distorted compared to impact on a static film.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation Into Droplet Impingement Upon Moving Films Using High Speed Video and Thermal Imaging

Mitchell

Simmons

Hann

2015

Volume 1: Advances in Aerospace Technology

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Aeroengine bearing chambers are geometrically complex, typically containing shafts, bearings, seals and stationary components. Oil is supplied for lubrication and cooling and so the chamber contains a highly rotating two-phase (oil/air) flow where the oil is typically present as droplets, ligaments, mist and films. These films may be thick or thin and film speed varies with chamber location. It is desirable to know a priori the outcome of a droplet-film impact event in terms of mass, momentum and energy transfer.There is a significant body of research on the interaction between droplets and static films. The experimental parameter space has been characterised on the basis of film thickness and impact parameter to predict the outcome of an impingement. The impingement of droplets on moving films has only begun to be investigated over the last decade and consequently models have not yet been developed and the parameter space has barely begun to be characterised.Within this paper results are presented from an experimental study in which water droplets of 3 mm and 3.8 mm at 20 • C falling under the influence of gravity impinged onto water films flowing down an inclined plane. Film temperature was 30 • C and film thicknesses were between 2.3 mm and 4.2 mm. High speed imaging was used to determine the impingement outcomes and cavity morphology. A high speed infrared camera was used to determine the extent of the thermally affected region and its temperature behaviour.We find that by using the resultant droplet velocity (combining droplet and film velocities) the film impingement outcomes can be characterised into regions very similar to those for static films. The data is presented as a function of splashing parameter and non-dimensional film thickness. It was observed that for these impacts on supercritical films (Fr > 1) there is less propensity for secondary droplet formation through jet breakup than on static and subcritical films (Fr < 1). Data was obtained for extent of the thermally affected region. It was found that the cooler droplet liquid spreads over the inside of the crater before heating up to film temperature. Development of crater shape and size was also studied and data compared to established models for droplet impact on deep static films. During the initial stages of an impact crater area increases similarly to that for static films although the crater shape itself is less similar and is asymmetrical due to the film motion.

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A Comprehensive Computational Fluid Dynamics Study of Droplet‐Film Impact and Heat Transfer

et al. 2015

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The Eulerian multiphase model and continuum surface force (CSF) are employed to simulate the liquid droplet impinging onto a solid wall with a pre-existing thin film of the same liquid. The numerical results are compared with the experimental data reported in the literature, indicating a reasonable matching. The flow field and splashing behavior of a droplet impinging onto a liquid film are analyzed. The reason for the edge of the crown to eject into secondary drops is found. The splashing behavior can be influenced by the impacting velocity and fluid properties. The effects of impact velocity, droplet diameter, depth of film, liquid property, and droplet and wall temperature on the heat removal are investigated. Numerical results demonstrate that an increase in impact velocity, droplet diameter, film depth, cooling droplet, and wall temperature enhances the dissipated heat. These results can provide a reference for designing spray-cooling systems.

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Normal droplet impact on horizontal moving films: an investigation of impact behaviour and regimes

Cited by 55 publications

References 25 publications

A study of droplet impact on static films using the BB-LIF technique

A study of droplet impact on static films using the BB-LIF technique

Experimental Investigation Into Droplet Impingement Upon Moving Films Using High Speed Video and Thermal Imaging

A Comprehensive Computational Fluid Dynamics Study of Droplet‐Film Impact and Heat Transfer

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