U.S.-Netherlands Cooperative Research on the Structure of a Turbulent Boundary Layer with Suction

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This award supports Assistant Professor Minami Yoda of Georgia Institute of Technology to collaborate in mechanical engineering research with Professor F.T.M. Nieuwstadt of the Laboratory of Aeroand Hydrodynamics of the Delft University of Technology, The Netherlands. Using particle imaging velocimetry, they will carry out a study of a turbulent boundary layer with and without suction in the vicinity of a few holes of a diameter of ten percent of the local boundary layer thickness. The Dutch laboratory has excellent experimental facilities for this research, and the experience with their set-up to be gained by the US PI will provide the basis for deciding whether and how to establish similar facilities at Georgia Tech. The two laboratories bring to the research effort complementary expertise in both hydrodynamic systems and specialized instrumentation: Delft in bounded flows and the application of particle imaging velocimetry and Georgia Tech in free shear flow control and laser-induced fluorescence. Turbulence increases drag (and operating cost) on moving surfaces such as airplane wings. Suction is known to re- laminarize and delay the separation of turbulent boundary layers, but too much suction can actually increase the separation. Suction through large holes or slots has been widely studied; smaller holes work better, but the cost of implementing has been found not to be worth the savings in drag. While new technology now permits economical production of minutely perforated surfaces, relatively little is known about the effect of suction on such small holes on the boundary layer structure. This work will help to clarify how such suction affects the coherent structures in the boundary layers, and increase understanding of `aerodynamic roughness`, where strong suction levels actually cause separation.