Droplet Impact on Thin Films: Vortex Ring Dynamics
Analysis
This paper investigates the fundamental fluid dynamics of droplet impact on thin liquid films, a phenomenon relevant to various industrial processes and natural occurrences. The study's focus on vortex ring formation, propagation, and instability provides valuable insights into momentum and species transport within the film. The use of experimental techniques like PIV and LIF, coupled with the construction of a regime map and an empirical model, contributes to a quantitative understanding of the complex interactions involved. The findings on the influence of film thickness on vortex ring stability and circulation decay are particularly significant.
Key Takeaways
- •Droplet impact on thin films generates vortex rings that govern momentum and species transport.
- •Film thickness significantly influences vortex ring stability, with thinner films promoting instability.
- •A regime map in Re-δ space characterizes the transition to unstable vortex structures.
- •Wall interactions in thinner films lead to faster decay of vortex ring circulation.
- •An empirical model is proposed to predict the temporal evolution of vortex ring circulation.
“The study reveals a transition from a single axisymmetric vortex ring to azimuthally unstable, multi-vortex structures as film thickness decreases.”