Collaborative Research: The Pressure Shielding of Aerodynamic Surfaces

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The surfaces of devices such as a wind turbine blade, of an airplane wing, of a propeller or fan are all designed to manage the flow of air in a beneficial way. However, turbulence that inevitably accompanies the flow produces pressure fluctuations on a surface that can result in undesirable vibration or sound. This research effort is directed at understanding how treatments placed just above a surface might be able to substantially reduce the pressure fluctuations, without negatively impacting the beneficial effects of a surface on the flow. The work will involve coordinated wind tunnel experiments at Virginia Tech, and theoretical studies at Florida Atlantic University. As well as advancing science and engineering in the area of fluid dynamics, the effort will be focused on the research training of PhD and undergraduate students. In particular the experiments will be integrated with required undergraduate laboratories at Virginia Tech, impacting several hundred students over the course of the project.The main objective of this work is to establish the fundamental scientific basis for surface treatments that reduce turbulent surface pressure fluctuations, while maintaining the wall-normal transport of momentum and low drag that is required in most fluid dynamic applications. Recent studies have definitively demonstrated that pressure shielding is possible. The purpose of this work is to provide a quantitatively usable fundamental understanding of the mechanisms behind these effects, and the mathematical methods needed for their prediction. The research program is focused on the application of pressure shielding treatments to two fundamental flows; the shear-free boundary layer formed adjacent to a wall in homogeneous turbulence, and a conventional flat plate turbulent boundary layer. These flows have been chosen since they cleanly separate some of the major mechanisms expected to be responsible for pressure shielding. They are also geometrically simple and well characterized, since analytical or experimental models of the complete correlation structure of these flows exist. Large scale experiments on these configurations with and without treatment, will be performed at Virginia Tech. Parallel mathematical modeling will be carried out at Florida Atlantic University. Through this closely linked study we expect not only to extract the fundamental nature of the pressure shielding, but also to build mathematically well-founded analytical tools needed for its prediction. A key goal is to provide research education to a diverse group of students drawn from a broad range of academic levels. The planned work includes specific tasks to be conducted by groups of undergraduate and high school students across both institutions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.