Modeling Fluid-Structure Interactions between Kirigami Sheets and Fluid Flow

This project will model the behavior of kirigami sheets placed in flow. Kirigami is the art of cutting thin sheets of material. It has found numerous applications in recent years, including soft robotics, structural mechanics, and material science. Recently, a series of experiments was conducted on kirigami sheets that were placed in a fluid flow. The sheets had three different categories of cut patterns. Depending on the cut pattern, several different flow-induced responses of the sheets were observed, corresponding to wake patterns in the flow. These experiments suggested that kirigami sheets could be useful in flow control, mixing, drag reduction, underwater soft robotics, and other applications. This project will conduct numerical simulations on kirigami sheets, derive models to predict their behavior in flow, and perform experiments to both inform and validate the models. The project will involve outreach programs to excite K-12 students to STEM careers, will incorporate research results into the college curriculum, and will hold an exhibition to display exciting scientific phenomena to the public, especially younger generations. Fluid flows that interact with the slits of a kirigami sheet constitute a multi-scale Fluid-Structure Interaction (FSI) engineering challenge. Small-scale FSI between one strip of the whole sheet should be understood and modeled properly, as the combined behavior of all these slits must be combined to understand and predict the wholistic behavior of a kirigami sheet in fluid flow. Previous investigations have shown how these small-scale interactions can have significant influences on the large-scale response of the structure, for example, resulting in dynamic flow-induced response instead of static response. This project will involve numerical simulations for both snapshots of deployed kirigami sheets and fully coupled FSI cases to capture both steady state and transient motions of the kirigami sheets interacting with the flow. Analytical models will be derived and validated with comparable experiments, which will enable a better understanding and predict capability for the behavior of kirigami sheets in fluid flow. A series of experiments will be conducted to understand the applicability of kirigami sheets for the suppression of flow-induced vibrations. Project outcomes will enable future use of kirigami-patterned sheets to reduce, or suppress, undesired flow-induced vibrations and drag and enhance mixing. 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.