The role of time in single drop splash on thin film

Abstract

This paper reports on an experimental study of\ud the impact of water drops on thin liquid films. The mor-\ud phology of the impact was studied by still photography,\ud and quantitative results were obtained by a proper image\ud analysis technique. The time evolution of various param-\ud eters like the crown diameter, the crown height, and the\ud secondary drop diameters are reported, and these experi-\ud mental parameters are correlated and compared to avail-\ud able theoretical models. A particular set-up of the\ud acquisition system allowed us to photograph the splash\ud from below the solid wall, allowing the first estimation of\ud the crown thickness and the total number of jets pro-\ud truding from the crown rim as a function of time. The\ud results indicate that, for the range of the parameters\ud investigated, there is not a strong dependence on the film\ud thickness. The evolution of the crown height depends on\ud the impact Weber number, whereas its growing velocity\ud and the crown thickness evolution are almost independent\ud of Weber number

Particle Image Velocimetry of Human Cough

“…High velocity coughs might be expected to have penetrated farther at this time, but in general the decay of jet speed with distance dominates. This is consistent with studies of transient turbulent jets (Johari et al 1997;Cossali et al 2004). The maximum normalized velocity is thus equal to 1 for each cough at each downstream distance.…”

“…Transient jets are observed to attain self-similarity after some development time and some distance downstream (L/D > 6) (Cossali et al 2004). However, at the early time and in the near field analyzed here, the average cough jet does not collapse well with this scaling, using the virtual origin defined by the half-height width.…”

“…Although the starting jet is acknowledged to be not self-similar, particularly in its initial stages and close to the head of the jet, experimental and theoretical analyses often explore the application of steadystate turbulent jet scalings. Several such recent works have had success in predicting the evolution of the tip of the jet (Johari et al 1997;Hill and Ouellette 1999;Song and Abraham 2003;Cossali et al 2004;Ai et al 2005;Bajpai and Tirumkudulu 2008).…”

Collisions of droplets on spherical particles

“…The measurements of Cossali et al (2004) determined that the maximum height of the crown for collisions of droplets on wet flat surfaces covered by a thin film and under the same Weber number as here (We ∼ 400) is about 35% greater than the droplet diameter. Considering the size of the examined droplets here, the prediction of Cossali et al (2004) gives a maximum height of about 300 µm, which is within 10% to the prediction of the POD analysis.…”

LBM Simulation of a Droplet Dripping Down a Hole

“…Experimental and numerical study about the impact of a droplet on a layer of the same liquid on a solid surface was presented by Pan and Law (2007). There are also some experimental studies which have been done in order to investigate the impact of droplets on a thin film layer (Cossali et al, 2004;Wal et al, 2006;Castanet et al, 2009). Krause et al (2011) simulated droplet formation and interaction in emulsification processes.…”