A Study Of Single Droplet Impacting On Moving Film And The Influence Factors

Study on droplet collision problem has important guiding significance for the lifeand production. In this paper, experiments were conducted on the foundation oftheories with visualization platform whose main member was high-speed camera, theliquid for the experiment were fresh water and glycerol-water mixture. The points ofthe study are the impacting properties like second droplet splash, crown, mid-jet andthe influencing factors with the droplet diameter, impact velocity, viscosity of the filmand the flow. The correlation between the impacting properties and the effects werediscussed deeply in the study.(1) The study on influence factors of the second droplet splash. The wholecollision processes were observed experimentally, to find out how droplet diameter,impact velocity, viscosity and the flow effected the droplet splash, experimentalresults were verified by numerical simulation. The result shows that, the biggerdroplet size and collision speed cause the more presumption of droplet splash, andwith the diameter of droplet and droplet collision speed increases, the number andvolume of splashing droplets are generated increases. But the viscosity and the flowof the film are in inhibitory effect, the bigger viscosity, the harder to generate dropletsplash, and a large liquid film flow gets less and smaller second droplet.(2) The study on influence factors of the crown. The development process of thecrown was studied by the method of experiment and confirmed by numericalsimulation. It points out that, the bigger droplet size and collision speed cause a highercrown in the impacting. And the maximum height of crown is linear growthrelationship with the impacting droplet diameter and the impacting velocity; Highviscosity of the liquid does not make any contributions to the height of crown, whenthe liquid viscosity becomes lower, for instance close to water, the crown height willbe much higher.(3) Analysis of the mid-jet’s height development and fracture mechanism. The factors of impacting droplet size, impact velocity, viscosity and film flow areconsidered to the mid-jet and the fracture mechanism. Similar with the crown, themaximum height of mid-jet is linear growth relationship with the impacting dropletdiameter and the impacting velocity; High liquid viscosity promotes the height ofmid-jet through reducing the energy loss. The higher impacting velocity and smallerviscosity of the experimental liquid, the more easily lead to the fracture of the mid-jet.