Title: Extensible membrane flutter and sail tacking in inviscid flow

Speaker: Dr. Christiana Mavroyiakoumou (Physique et Mécanique des Milieux Hétérogènes Lab, ESPCI Paris)

Room: 004

Abstract: In this talk, I’ll consider two problems in fluid dynamics: the physics of a sailing maneuver as a fluid-structure interaction problem, and the passive interactions between an extensible, rectangular membrane and inviscid fluid flow. First, I will explore how flexible sails behave during a tacking maneuver — when a sail turns into the wind to achieve upwind sailing. Sometimes the sail successfully flips into its mirror-image shape; other times, it gets stuck close to its initial shape, unable to flip. I will demonstrate what determines a successful flip and how long it takes, focusing on both the sail's material properties and how the maneuver is executed. I will also show that stiffness, tension, and final sail angle to the wind play the biggest roles in whether the flip happens at all, while the sail's mass and the speed and acceleration of the turn mostly affect how fast the flipping happens. Second, I will talk about rectangular membranes with deflections that have significant spanwise nonuniformity and that shed a trailing vortex-sheet wake when immersed in a three-dimensional inviscid fluid flow. Examples include textile fabric, rubber, or the skin of swimming and flying animals.