Dynamics in thin sheets in flow: flipping, folding, bending and buckling

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CBET - 1604767PI: Graham, Michael D.Flows involving suspensions of particles in a liquid are frequently encountered in manufacturing of many consumer products and in naturally occurring systems. Understanding the detailed motion of the suspended particles can be used to predict the material properties and behavior of the suspension as a whole. This information can be used by engineering practitioners to design processes to achieve desired properties in products ranging from familiar household goods to highly specialized materials. This project involves numerical computations aimed at understanding the motion of thin flexible sheets that are freely suspended in a viscous liquid. When suspended in flow, the thin sheets, which are often the precursors of the final material, can exhibit a variety of interesting motions, all of which must be understood in order to form the sheets into desired shapes. The project will use computational methods based on fundamental equations that govern the motion of the fluid and the mechanical properties of the sheets to analyze the motion of the sheets and the dynamics of the suspension. The project will provide opportunities for students at various academic levels to participate in research. Students, especially those form groups traditionally underrepresented in science and engineering, will be recruited to the project from programs at the University of Wisconsin. In addition, the investigators will participate in developing hands-on demonstrations of fluid mechanics principles in action for K-12 students through local Boys and Girls Clubs. They will enlist and train undergraduate and graduate students to participate as mentors for the youngsters. Numerical methods that have been used to analyze deformable particles in flow will be adapted for calculating the dynamics of freely suspended flexible sheets in canonical flows such as simple shear and extensional flow. The motion of the sheets and networks of sheets will be correlated with their rest shapes and the characteristics of the flow. The effect of bending stiffness and the possible formation of creases will be investigated and exploited to determine whether the sheets can be forced by the flow into forming structures such as simple cubes. Simple models of bistable elastic structures in flow will be examined to quantify interactions between sheet elasticity and flow. The results of the project will provide useful information to help analyze fabrication of electronic and polymeric materials that are processed as thin sheets.