This is a past event.

Michigan Tech's Assistant Professor Hassan Masoud (MEEM) will be presenting at the next Physics Colloquium. Please join the in-person presentation at 4:00 p.m. Thursday (Dec 8) in Fisher Hall 139.

MARANGONI SURFING: FROM THEORY TO APPLICATION

Abstract: We study the surfing motion of chemically-active objects along a flat liquid-gas interface. The objects are self-propelled by means of creating and maintaining a surface tension gradient resulting from an asymmetric release of a chemical agent. We use theory, numerical simulation, and experiments to examine the propulsion of these Marangoni surfers. First, we consider the behavior of simple surfers at a wide range of release rates and diffusivity of the exuded chemical species (that set the effective Reynolds and Peclet numbers), and subject to various degrees of confinement represented by the thickness of the liquid film. We show that the surfers can undergo a forward, backward, or an arrested motion, and identify the link between these modes of mobility and the flow structure in the vicinity of the surfers. We also find, perhaps surprisingly, that there exist certain intermediate Reynolds and Peclet numbers at which the propulsion speed of the surfers reaches a peak. Next, we focus on the dynamics of a self-powered and remotely controlled robot, which is inspired by water-walking insects and uses the Marangoni effect for both forward motion and change of direction. We analyze the performance of this surfing robot (characterized by its speed, fuel efficiency, and maneuverability) and showcase its novel capabilities. Overall, the findings of our investigations provide new insights into the propulsion of Marangoni-driven surfers and help establish engineering guidelines for their efficient design and effective operation.

Bio: Dr. Masoud received his Ph.D. in Mechanical Engineering from the Georgia Institute of Technology and conducted post-doctoral research under the joint supervision of Howard Stone in the Department of Mechanical and Aerospace Engineering at Princeton University and Michael Shelley at the Courant Institute of Mathematical Sciences, NYU. Since July 2017, he has been an Assistant Professor in the Department of Mechanical Engineering-Engineering Mechanics at Michigan Tech. Dr. Masoud leads the Complex Fluids and Active Matter Lab, where he and his team employ the tools of applied mathematics and experiments to fundamentally understand the interaction of fluid flows with dynamically changing boundaries at a wide range of length and time scales. Their goal is to integrate the acquired fundamental understanding with engineering ideas to address outstanding technological and societal problems. Dr. Masoud’s research has been supported by the National Science Foundation, through including a recent CAREER award