Collaborative Research: Actuating and Sensing Objects on a Free Surface

This collaborative research investigates the strong coupling between floating particles at the air-water interface and water waves, which is a fundamental scientific problem with inspiration for technological innovation. The water surface in nature attracts all sorts of objects, such as biological organisms in search of food and mates, as well as microplastics and oil spills polluting the world's oceans and lakes.

Thus, the water surface provides an important opportunity to survey the local ecology and clean the pollutants if one can identify and control these objects on-demand. The outcomes of this project will provide fundamental understanding of physical mechanisms necessary for such applications, which range from locating floating objects in darkness for search and surveillance missions, to collecting marine debris for environmental protection.

In addition, the PIs will participate in various educational activities at their home institutions with a focus on recruiting students from under-represented groups. The students participating in this research will be trained in both experimental and theoretical approaches and will engage in active collaboration across institutes through co-advising, virtual group meetings, and presentations.

The overall objective of this collaborative research is to gain fundamental understanding of rich dynamical interactions that arise between the floating objects, surface waves and fluid flows. Specifically, the PI team will uncover complex particle-wave interactions in the context of sensing and controlling objects at the fluid-fluid interface. There are different types of hydrodynamic interactions that dominate depending on the relevant length scale of the system.

For example, wave dispersion and particle movement on a thin liquid layer are governed by capillary and viscous forces, while the wave-particle dynamics on the deep water surface is governed primarily by inertia and gravity. However, there is no comprehensive framework at present that can resolve the coupled dynamics of the surface waves and particles at the interface across different scales.

By combining experiments and mathematical modeling, the four PIs will investigate the fundamentals of wave-particle interactions: sensing (scattered waves) and actuation (force and torque) of floating objects remotely, in the distinct limits of shallow and deep water waves.

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.