FY2010 - Oak Ridge National Laboratory

05884
Drag Reduction with Superhydrophobic Surfaces
Charlotte Barbier and Brian D’Urso
Seed Money Fund—
Computational Sciences and Engineering Division
Project Description
Superhydrophobic surfaces such as leaves of a lotus plant consist of a hydrophobic surface combined with
microstructures or protrusions. These surfaces are extremely difficult to wet, and recently they have been
shown to reduce drag in water flow. However, their drag reduction has been investigated mainly in the
laminar region (small objects, small velocity), and few data are available in the turbulent regime (larger
objects, larger velocity), where most practical applications are.
We will fabricate a new generation of superhydrophobic material that will combine both microscale and
macroscale features for optimizing drag reduction in the turbulent regime. These materials will be tested
in the Center for Nanophase Materials Sciences (CNMS) with a cone-plate rheometer. In parallel,
numerical tools will be developed and validated on these measurements. They will be then used to
demonstrate the capabilities of these materials for practical applications such as pipelines or seafaring
vessels.
Mission Relevance
The scope of this work is consistent with DOE’s commitment to nanotechnology research and
development as well as to advanced computational methods. This research will expand the application of
superhydrophobic surfaces for drag reduction in pipelines, on ships, and in many other contexts. In so
doing, it creates the potential for substantial energy savings in the wide range of applications where drag
creates energy losses. Thus, it is well aligned with DOE objectives.
An efficient drag reduction technology will be particularly useful to the Department of Defense or Office
Naval of Research for their vessels, and the Department of Agriculture for irrigation applications.
Results and Accomplishments
The slip boundary condition was implemented in OpenFOAM and validated with theory. A series of
calculations was run for two different slip lengths (25 and 50 m) for a cone-and-plate geometry.
Convergence of the calculations was improved by writing an application that maps the fields from one
case to another by multiplying the pressure and velocity fields with an appropriate factor. For the
experimental part, a rheometer was identified at CNMS and the experimental setup was designed. The
work done during FY 2010 is on the right track to achieve the goals planned for FY 2011.
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