Title

Multimodal Shape Oscillations Of Droplets Excited By An Air Stream

Keywords

Fluid viscosity; Pendant droplet; Shape oscillations; Vibrational modes

Abstract

The shape dynamics of droplets exposed to an air jet at intermediate droplet Reynolds numbers is investigated. High speed imaging and hot-wire anemometry are employed to examine the mechanism of droplet oscillation. The theory that the vortex shedding behind the droplet induces oscillation is examined. In these experiments, no particular dominant frequency is found in the wake region of the droplet. Hence the inherent free-stream disturbances prove to be driving the droplet oscillations. The modes of droplet oscillation show a band of dominant frequencies near the corresponding natural frequency, further proving that there is no particular forcing frequency involved. In the frequency spectrum of the lowest mode of oscillation for glycerol at the highest Reynolds number, no response is observed below the threshold frequency corresponding to the viscous dissipation time scale. This selective suppression of lower frequencies in the case of glycerol is corroborated by scaling arguments. The influence of surface tension on the droplet oscillation is studied using ethanol as a test fluid. Since a lower surface tension reduces the natural frequency, ethanol shows lower excited frequencies. The oscillation levels of different fluids are quantified using the droplet aspect ratio and correlated in terms of Weber number and Ohnesorge number. © 2014 Elsevier Ltd.

Publication Date

7-26-2014

Publication Title

Chemical Engineering Science

Volume

114

Number of Pages

85-93

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.ces.2014.04.019

Socpus ID

84899908516 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84899908516

This document is currently not available here.

Share

COinS