Single-drop impingement onto a wavy liquid film and description of the asymmetrical cavity dynamics.

Nils Paul van Hinsberg,Marie Charbonneau-Grandmaison

doi:10.1103/physreve.92.013004

Abstract

The present paper is devoted to an experimental investigation of the cavity formed upon a single-drop impingement onto a traveling solitary surface wave on a deep pool of the same liquid. The dynamics of the cavity throughout its complete expansion and receding phase are analyzed using high-speed shadowgraphy and compared to the outcomes of drop impingements onto steady liquid surface films having equal thickness. The effects of the surface wave velocity, amplitude and phase, drop impingement velocity, and liquid viscosity on the cavity's diameter and depth evolution are accurately characterized at various time instants. The wave velocity induces a distinct and in time increasing inclination of the cavity in the wave propagation direction. In particular for strong waves an asymmetrical distribution of the radial expansion and retraction velocity along the cavity's circumference is observed. A linear dependency between the absolute Weber number and the typical length and time scales associated with the cavity's maximum depth and maximum diameter is reported.

Highlights

The fluid mechanics behind impingements of drops on dry or wetted surfaces has a great relevance in a large variety of technical, ecological, agricultural, and meteorological fields
This section focuses in detail on the results of the singledrop impingement experiments that are used to study the effect of traveling solitary surface waves on the diameter and depth evolution of the cavity in time
Smaller differences of the solitary wave amplification and higher values of the Reynolds number for both liquids lead to negligible effects of the viscosity on the cavity dynamics, in agreement with the results presented in [25] for the impingement onto steady surface films of finite thickness

Summary

Introduction

The fluid mechanics behind impingements of drops on dry or (partially) wetted surfaces has a great relevance in a large variety of technical, ecological, agricultural, and meteorological fields. Specific applications can for example be found inside gas turbines, for spray drying, coating of metallic products [1] and cooling, in medical applications and forensic investigations, as well as the electrification inside waterfalls [2], during thunderstorms [3], soil erosion [4], and in the dispersion of seed and microorganisms. For most of these applications the splashing of drops on thin liquid layers, the latter ones possessing a morphology that is both locally and globally highly dynamic, influences the flow behavior.

Methods

Results

Conclusion