This Interdisciplinary Research project presents a new concept for surfaces interacting with fluids - flexible surfaces that can be designed to hydroelastically or aeroelastically interact with boundary-layer flow in a favorable manner leading to reduction of drag forces. The basic idea, which is inspired by condensed matter physics, is to have a periodic lattice structure at the inner core of the surface, hence the phrase phononic surface. The surface will be primarily designed to delay laminar-to-turbulence transition and separation, and also to cause drag reduction for fully developed turbulent flow. Other functions that can be simultaneously realized are reduction of overall vibrations and structural noise emission. The research plan involves investigation of an efficient, systematic and integrated methodology for modeling, analysis and design of the proposed phononic surfaces. For the periodic lattice unit cell band structure calculation, a novel and efficient computational scheme based on modal analysis will be utilized. Specialized genetic algorithm operators will be created for the unit cell optimization. Direct numerical simulation of the flow and the elastic wave motion in the surface will be carried out. The unit-cell design will be performed independently of the full coupled solid-fluid simulations thus providing crucial computational savings.

The interdisciplinary nature of the research, at the cross-roads of dynamical systems, condensed matter physics and fluid dynamics will enrich the various aspects of the planned research. Elucidating the nature of the interaction between the dispersive periodic waves in and beneath the solid surface and the nonlinear and unstable fluid waves will constitute a new discovery involving fundamental physical phenomena. The subsequent utilization of this knowledge promises to open a new direction in flow control. For streamlined ships and aircrafts, or vehicles in general, the proposed drag-reduction concept will bring about substantial improvements in fuel efficiency and hence economic and environmental benefits. Gains to the performance of turbines of different sorts could also be realized.

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University of Colorado at Boulder
United States
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