Marangoni shocks in unobstructed soap-film flows.
It is widely thought that in steady, gravity-driven, unobstructed soap-film flows, the velocity increases monotonically downstream. Here we show experimentally that the velocity increases, peaks, drops abruptly, then lessens gradually downstream. We argue theoretically and verify experimentally that the abrupt drop in velocity corresponds to a Marangoni shock, a type of shock related to the elasticity of the film. Marangoni shocks induce locally intense turbulent fluctuations and may help elucidate the mechanisms that produce two-dimensional turbulence away from boundaries.
Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois 61801, USA.
Tuan
T
Tran
Pinaki
P
Chakraborty
Gustavo
G
Gioia
Stanley
S
Steers
Walter
W
Goldburg