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Systematic Design of Feedback Flow Control for Turbulent Drag Reduction

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Taming turbulence: we develop systematic approaches to design flow control schemes to reduce drag on the next generation of ships, airplanes and other engineering systems.

Reducing turbulent drag on engineering surfaces such as ship hulls or pipes has the potential of tremendous energetic savings. For example, a moderate 30% reduction of turbulent drag on ocean ships would reduce the fuel consumption by 7x108 barrels of oil annually in the ocean shipping industry alone (McKeon et al., 2013). Yet, a systematic, model-based approach for analyzing and designing drag reduction mechanisms such as feedback flow control is currently missing in the literature. We use the resolvent analysis developed by McKeon & Sharma to formulate the first-of-a-kind systematic approach to the design of turbulent drag reduction mechanisms. The approach is outlined by the example of feedback flow control and validated using DNS. Our results thus far show that the resolvent model is able to predict the response of the full nonlinear system to control and suggest that the model is accurate enough for controller design. Our current research efforts focus on systematic, model-based design of novel control schemes suitable for practical applications.

Figure: Coherent structures in a turbulent channel flow. The motions associated with these structures are responsible for a large amount of drag on engineering surfaces. 

Simon Toedtli, Beverley McKeon

AFOSR FA 9550-16-1-0361