This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
CBET -0853657 Papavassiliou, Dimitrios V.
This project will investigate the fundamental molecular mechanisms that can result in fluid slip at a solid-fluid interface and how exactly, if at all, fluid slip affects the structure of turbulence away from the viscous wall sublayer. It has been recently documented that ultra-hydrophobic surfaces induce slip in fluids moving over them. For laminar flows, this slip at the wall results in drag reduction that has been observed both experimentally and computationally. Recent computational work shows that ultra-hydrophobic surfaces can lead to turbulent drag reduction only when they result in significant fluid slip at the wall. Turbulent drag reduction has been achieved with the introduction of a very small amount of additives, such as polymers, surfactants or microbubbles. Such methods are mainly feasible for internal flows. However, when a fluid flows around an object, the use of additives to alter the fluid properties is at best impractical. If treating a conduit (or a vehicle) surface such that it becomes ultra-hydrophobic can result in drag reduction, then such treatment will present a drag-reduction technology feasible for both internal and external flows. This study is focused on the fundamental investigation of the conditions that generate fluid slip at the solid-water interface, and the effects that such slip can have on turbulence drag reduction. Specific issues to be investigated include the correlation between hydrophobicity and fluid slip and its interpretation based on the molecular structure of the fluid next to a solid-fluid interface, the exploration of the type of fluid and the type of interface that can result in fluid slip, and the determination of the mechanism by which slip affects the generation and maintenance of turbulence. These findings will be significant for the theory of fluid flow next to solid surfaces and for turbulence, as well as for many industrial applications. Aspects of this research project will be instrumental in the development of a new course and will be integrated in existing courses. In addition, the database generated through this project will become available to the community through existing web servers, and databases that can serve as validation benchmarks are planned.
