Asymmetrical morphological evolution and energy conversion of droplets impacting on the moving film

Droplet impacting on the film has been an important research topic, which is relevant to many important industries and is of high utilization value. The droplet impacting process shows excellent mass and heat transfer capability, whereas the liquid film is often in a flowing state, the morphological deformation and energy conversion of successive droplets impacting a moving liquid film were investigated. A three-dimensional volume of fluid model coupled with level-set function was established to investigate the single and successive droplet impact on the moving film. The asymmetry dynamic and energy dissipation and in the morphological evolution of the simultaneous single and successive droplet impacting processes under different droplet Weber numbers Wed and film Reynolds numbers Ref were thoroughly investigated. With smaller Wed and larger Ref, the liquid sheet downstream of the crown is more suppressed and the asymmetry of the crown is more significant. When Ref is constant, the dimensionless radius of the crown is related to the Wed0.2 and also to the power of dimensionless time, with the exponents differing between the upstream and downstream. The relationship of energy dissipation with dimensionless number was discussed, in which the kinetic energy Ek reduction accounts for a major part of the dissipation even though the surface energy Es increases due to the formation of the crown. Additionally, the upstream liquid sheets merging of the inner and outer crowns due to successive droplets continuous impacting on the moving film were also observed. With larger Ref and lower impingement frequency, the merging of the upstream liquid sheets is earlier.