How does the surrounding gas cause an impacting drop to splash? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
How does the surrounding gas cause an impacting drop to splash?
Plain
A drop hitting a smooth dry surface in air throws off a thin sheet that breaks into droplets, but in thin enough air the same impact does not splash at all. How the air produces the splash is not agreed.
Precise · changed · core
Revision 1: A low-viscosity drop of radius $R \sim 0.1\,\mathrm{cm}$ hitting a smooth dry solid at speed $V$ of a few hundred cm/s splashes at 1 atm but not below a threshold gas pressure $P_{T}$ (Xu, Zhang, Nagel, PRL 2005). Identify the gas-mediated force that lifts the thin liquid sheet ejected near the contact line, and derive P_T(V, R, liquid viscosity, gas mean free path) together with the time and position of sheet ejection.
Revision 2: A low-viscosity drop of radius $R \sim 0.1\,\mathrm{cm}$ hitting a smooth dry solid at speed $V$ of a few hundred cm/s splashes at 1 atm but not below a threshold gas pressure $P_{T}$ (Xu, Zhang, Nagel, PRL 2005). Identify the gas-mediated force that lifts the thin liquid sheet ejected near the contact line, and derive $P_{T}$(V, R, liquid viscosity, gas mean free path) together with the time and position of sheet ejection.
Settled by
Simultaneous measurement of gas-film thickness, sheet ejection time and $P_{T}$ across gases and liquid viscosities, matched by a theory without fitted parameters.
Kind
phenomenon
Answer type
mechanism
References
(empty)
Literature status
contested
Status note
Competing models invoke aerodynamic lift on the advancing sheet (Riboux and Gordillo 2014) and Kelvin-Helmholtz instability of a thin air film (arXiv:1509.01230); none is confirmed over the full parameter range.
Posed since
2005

Decisions