This award will support a 24 month long-term visit by Dr. Stanley Skebe, Aerodynamics and Environmental Sciences Division, United Technologies Research Corporation (UTRC), Hartford, Connecticut, to Japan for a cooperative research project with Professor Shunichi Tsuge, Institute of Engineering Mechanics, University of Tsukuba. The research will include a study of the effect of vortex generation devices on diffuser performance. The focus would be to conduct an experimental investigation into the application of several standard and advanced vortex generator shapes within a family of rectangular diffuser geometries and over a range of flow parameters and to quantify their ability to alleviate diffuser stall and improve diffuser performance through mixing enhancement. Supporting theoretical calculations, based on 'first principles' analyses, would also be performed. Smoke trace, tuft motion, and surface oil flow visualization techniques would be used to document diffuser stall reduction while pneumatic pressure transducer measurements would yield diffuser pressure coefficient values upon which to base performance improvement. Finally, they will undertake a detailed boundary layer survey and state-of-the-art laser sheet flow visualization measurements. These measurements are expected to broaden the applicability of the program results and deepen their significance with respect to the field of fluid mechanics by providing a fundamental understanding of the effect of embedded axial vortex arrays on adverse pressure gradient boundary layer flow separation characteristics. Diffusers see frequent component application in a wide variety of fluid dynamic-based products, such as consumer appliances, home and building air handling systems, chemical plants, automobile components, and aircraft engines. They are also often the key product component, with their efficiency level restricting the upper limit of overall product efficiency. Improved diffuser designs could improve product performance and allow for a reduction in product noise generation and/or energy consumption. This research combining United Technologies Research Center's accumulated experience on vortex generation and forced mixing flowfields with the University of Tsukuba's theoretical and experimental experience on the behavior of vortex generation should provide a productive climate for advancing the research in this important area. It is expected that this collaborative effort will continue after the formal agreement has terminated.
