Levich Institute Seminar Announcement, 02/23/2010
Tuesday, 02/23/2010
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Jonathan Rothstein
University of Massachusetts
Department of Mechanical and Industrial Engineering

"Laminar and Turbulent Drag Reduction Using Superhydrophobic Surfaces "


ABSTRACT


A series of experiments and direct numerical simulations (DNS) will be presented which demonstrate significant drag reduction for both laminar and turbulent flows of water through channels using superhydrophobic surfaces with well-defined micron-sized surface roughness. The surfaces are fabricated from PDMS to incorporate precise patterns of ridges or posts that can support a shear-free air-water interface. A flow cell is used to measure the pressure drop and velocity profile as a function of the flow rate for a series of channel geometries and superhydrophobic surface designs. DNS are performed for flow past superhydrophobic surfaces which both complement and extend the range of geometries and Reynolds number obtained in the experiments. We will show that drag reductions up to 75% and slip lengths up to 150mm can be obtained in turbulent flows past superhydrophobic surfaces. Additionally, we will show that slip along the air water interface forestalls the transition from laminar to turbulent flow. The drag reduction is found to increases with increasing post/ridge spacing and the fraction of air-water interface. In turbulent flows, the drag reduction increases with Reynolds number before eventually reaching a plateau. These results suggest that in turbulent flows, the drag reduction scales with the thickness of the viscous sublayer and not the overall channel height as in laminar flows.

BRIEF ACADEMIC/EMPLOYMENT BACKGROUND:

Ph.D. from MIT in 2001, M.S. from Harvard in 1998, B.Eng. from Cooper Union in 1996. Assistant Professor University of Massachusetts Mechanical Engineering 2001-2007, visiting Professor of Chemical Engineering Katholieke Universiteit in Leuven, Belgium 2007-2008, Associate Professor University of Massachusetts Mechanical Engineering 2007-present.

RECENT RESEARCH INTERESTS:

Non-Newtonian fluid dynamics, rheology, drag reduction, microfluidics, polymer processing, surfactant solutions, suspensions, self-assembly, nanomanufacturing