The Feynman Sprinkler Problem

Flows with inertia are not reversible, a fact that has many surprising consequences and practical applications. I'll discuss several curious cases and mainly focus on the infamous reverse sprinkler problem that has attracted the likes of Mach and Feynman. The problem was stubbornly resisted an answer for 140 years and left a literature full of contradictory observations, conflicting predictions, and passionate disagreements. I'll talk about what our precision experiments tell us and how math modeling and flow simulations are helping to make sense of the results.

Our first findings were recently published, but there is much more to do.
 

Bio:
Leif Ristroph is an associate professor of mathematics at The Courant Institute, New York University. He is an experimental physicist and applied mathematician who specializes in fluid dynamics, with a particular emphasis on fluid-structure interactions as applied to biological and geophysical flows. His biophysical work includes studies of the aerodynamics and stabilization of insect flight as well as the hydrodynamics of schooling and flow-sensing in swimming fish. Relevant to geophysical flows, he is interested in problems ranging from instabilities of interfacial flows to the evolution of shape during fluid mechanical erosion.