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Splash wave and crown breakup after disc impact on a liquid surface

Splash wave and crown breakup after disc impact on a liquid surface
Splash wave and crown breakup after disc impact on a liquid surface
In this paper we analyse the impact of a circular disc on a free surface using experiments, potential flow numerical simulations and theory. We focus our attention both on the study of the generation and possible breakup of the splash wave created after the impact and on the calculation of the force on the disc. We have experimentally found that drops are only ejected from the rim located at the top part of the splash – giving rise to what is known as the crown splash – if the impact Weber number exceeds a threshold value Wecrit?140. We explain this threshold by defining a local Bond number Botip based on the rim deceleration and its radius of curvature, with which we show using both numerical simulations and experiments that a crown splash only occurs when Botip?1, revealing that the rim disrupts due to a Rayleigh–Taylor instability. Neglecting the effect of air, we show that the flow in the region close to the disc edge possesses a Weber-number-dependent self-similar structure for every Weber number. From this we demonstrate that Botip?We, explaining both why the transition to crown splash can be characterized in terms of the impact Weber number and why this transition occurs for Wecrit?140. Next, including the effect of air, we have developed a theory which predicts the time-varying thickness of the very thin air cushion that is entrapped between the impacting solid and the liquid. Our analysis reveals that gas critically affects the velocity of propagation of the splash wave as well as the time-varying force on the disc, FD. The existence of the air layer also limits the range of times in which the self-similar solution is valid and, accordingly, the maximum deceleration experienced by the liquid rim, that sets the length scale of the splash drops ejected when We>Wecrit.
0022-1120
553-580
Peters, Ivo R.
222d846e-e620-4017-84cb-099b14ff2d75
van der Meer, Devaraj
54e00557-0050-43f5-9efb-a28ea962591c
Gordillo, J.M.
da39af29-e973-4dd1-ae65-56465f331ac2
Peters, Ivo R.
222d846e-e620-4017-84cb-099b14ff2d75
van der Meer, Devaraj
54e00557-0050-43f5-9efb-a28ea962591c
Gordillo, J.M.
da39af29-e973-4dd1-ae65-56465f331ac2

Peters, Ivo R., van der Meer, Devaraj and Gordillo, J.M. (2013) Splash wave and crown breakup after disc impact on a liquid surface. Journal of Fluid Mechanics, 724, 553-580. (doi:10.1017/jfm.2013.160).

Record type: Article

Abstract

In this paper we analyse the impact of a circular disc on a free surface using experiments, potential flow numerical simulations and theory. We focus our attention both on the study of the generation and possible breakup of the splash wave created after the impact and on the calculation of the force on the disc. We have experimentally found that drops are only ejected from the rim located at the top part of the splash – giving rise to what is known as the crown splash – if the impact Weber number exceeds a threshold value Wecrit?140. We explain this threshold by defining a local Bond number Botip based on the rim deceleration and its radius of curvature, with which we show using both numerical simulations and experiments that a crown splash only occurs when Botip?1, revealing that the rim disrupts due to a Rayleigh–Taylor instability. Neglecting the effect of air, we show that the flow in the region close to the disc edge possesses a Weber-number-dependent self-similar structure for every Weber number. From this we demonstrate that Botip?We, explaining both why the transition to crown splash can be characterized in terms of the impact Weber number and why this transition occurs for Wecrit?140. Next, including the effect of air, we have developed a theory which predicts the time-varying thickness of the very thin air cushion that is entrapped between the impacting solid and the liquid. Our analysis reveals that gas critically affects the velocity of propagation of the splash wave as well as the time-varying force on the disc, FD. The existence of the air layer also limits the range of times in which the self-similar solution is valid and, accordingly, the maximum deceleration experienced by the liquid rim, that sets the length scale of the splash drops ejected when We>Wecrit.

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More information

Accepted/In Press date: 18 March 2013
e-pub ahead of print date: 29 April 2013
Published date: June 2013
Organisations: Aerodynamics & Flight Mechanics Group

Identifiers

Local EPrints ID: 400140
URI: http://eprints.soton.ac.uk/id/eprint/400140
ISSN: 0022-1120
PURE UUID: b2cb6b31-8600-45b3-8312-3fc4ddae3e61
ORCID for Ivo R. Peters: ORCID iD orcid.org/0000-0002-3549-3322

Catalogue record

Date deposited: 20 Sep 2016 13:20
Last modified: 22 Nov 2021 03:08

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Contributors

Author: Ivo R. Peters ORCID iD
Author: Devaraj van der Meer
Author: J.M. Gordillo

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