New paper: Rising arches in floppy chains

A chain initially lying in a pile is pulled rapidly from one end. A hump of chain forms spontaneously then grows slowly in height. The hump forms at the transition between two distinct regions of chain, one moving rapidly at constant velocity and the other motionless on the table. A chain moving along itself, in the absence of external forces, can support any shape by maintaining a constant stress. This is the basis of the “lariat chain” demo, which you can see at the San Francisco exploratorium. We have formulated a qualitative model of the formation of the hump, which combines the lariat solutions, noise, and the action of the table which acts as a noise rectifier constantly lifting the chain up.

You can view a video of the phenomenon from a 2011 “Gallery of Fluid Motion” video located here.

J.A. Hanna and C.D. Santangelo, “Slack dynamics on an unfurling string,” to appear Physical Review Letters, [ARXIV] (2012).