Abstract
An efficient time-adaptive multigrid algorithm is used to solve a range of normal and oblique droplet impacts on dry surfaces and liquid films using the Depth-Averaged Form (DAF) method of the governing unsteady Navier–Stokes equations. The dynamics of a moving three-phase contact line on dry surfaces is predicted by a precursor film model. The method is validated against a variety of experimental results for droplet impacts, looking at factors such as crown height and diameter, spreading diameter and splashing for a range of Weber, Reynolds and Froude numbers along with liquid film thicknesses and impact angles. It is found that, while being a computationally inexpensive methodology, the DAF method produces accurate predictions of the crown and spreading diameters as well as conditions for splash, however, underpredicts the crown height as the vertical inertia is not included in the model.
Highlights
Droplet impacts appear in a variety of engineering applications that would benefit from an improved understanding of the droplet-film interactions, allowing for optimisation of the impact behaviour for any particular situation
A droplet will be impacting upon a dry surface which quickly changes into a thin liquid film created by deposition of the previous droplets [1]
The dynamics of droplet impacts on dry surfaces are modelled by a precursor film model [51] that assumes the presence of a thin uniform liquid layer of thickness h∗ preceding and surrounding the droplet and covering the substrate
Summary
Droplet impacts appear in a variety of engineering applications that would benefit from an improved understanding of the droplet-film interactions, allowing for optimisation of the impact behaviour for any particular situation. A droplet will be impacting upon a dry surface which quickly changes into a thin liquid film created by deposition of the previous droplets [1]. This is the case in spray painting, surface cleaning and ink-jet printing where achieving a large droplet spread without splashing is desirable [2]. For the case of fuel injection within internal combustion engines, splashing may be desirable to create secondary atomisation and increase the fuel vaporisation rate. An abundance of research has been carried out to validate that the behaviour
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