Capillary wave under shear

It is known the thermally excited capillary wave can make a liquid-gas interface rough.

We also know wind flowing past a water surface make the surface rough.

Surprisingly, researchers show that the shear like wind suppress the roughness in liquid-gas interface instead of  increasing.

This phenomenon can be described by introducing an effective interfacial tension that increases with the shear rate.

The increase  is a direct consequence of the loss of interfacial entropy caused by the flow,

which affects especially the slow fluctuations. This demonstrates that the

interfacial tension of fluids results from an intrinsic as well as a fluctuation contribution.

For more details, see

Derks D, Aarts D G A L, Bonn D, et al. Suppression of thermally excited capillary waves by shear flow[J]. Physical review letters, 2006, 97(3): 038301.