Oblique Impacts of Nanodroplets upon Surfaces.

Abstract

In this work, oblique impacts of nanodroplets impacting surfaces in a wide range of impact angles (α) are investigated in detail via molecular dynamics simulations. Five outcomes are observed, including deposition, prompt splashing, break-up, separation, and shattering. With increasing impact angle, the outcomes of prompt splashing, break-up, separation, and shattering are enlarged but the one of deposition is compressed. By drawing a Wen ∼ α phase diagram, the outcome regimes and corresponding boundaries of them can be successfully identified, and the boundary between the deposition and other outcome regimes is theoretically modeled and shows good agreement with the phase diagram, where Wen is the normal impact Weber number. For further understanding of the oblique impacts, the maximum spreading factor, as the feature parameter of spreading, is investigated. Asymmetry spreading behaviors are observed, noting that βmax,∥ is always larger than βmax,⊥. βmax,⊥ is tested that it only depends on Wen with wide impact angles and could be predicted by the scaling law of βmax,⊥ = 0.7Wen1/4. However, βmax,∥ depends on not only Wen but also impact angles. A modified model is proposed for predicting βmax,∥ as 0.7Wen1/4 + 0.001(Wen tan2 α)3/2, which shows good agreement with data on surfaces with θ from 73 to 105° in wide Wen and α ranges.