Fluctuations and stratification in sedimentation of dilute suspensions of spheres

Daniel Chehata Gómez, Laurence Bergougnoux, Élisabeth Guazzelli, and John Hinch

Whether stratification can control velocity fluctuations in suspensions of sedimenting spheres is tested. The initial value and early decay of the velocity fluctuations are not affected by stratification. On the other hand, in the descending front where the stratification is strong and well defined, the velocity fluctuations are inhibited according to a previously proposed scaling. In between, after the initial decay and before the arrival of the front, the local value of the stratification does not always play a role.

Phys. Fluids 21, 093304 (2009)

Drag reduction in turbulent flows over superhydrophobic surfaces

Robert J. Daniello, Nicholas E. Waterhouse, and Jonathan P. Rothstein

This paper demonstrates that periodic, micropatterned superhydrophobic surfaces, previously noted for their ability to provide laminar flow drag reduction, are capable of reducing drag in the turbulent flow regime.

Phys. Fluids 21, 085103 (2009) | Physics Today