Synopsis: Coiling Viscous Jets

A new model can predict the patterns formed by a viscous jet falling onto a moving surface.
Synopsis figure
Pierre-Thomas Brun/MIT

When poured onto toasted bread, honey can deposit in a variety of wavy patterns, like meanders, loops, or coils. Similar coiling patterns are seen in a variety of systems, ranging from jets for 3D printing to underwater optical fibers. But, to date, no theoretical models have been able to explain the complex features observed in experiments. Now, a team led by Pierre-Thomas Brun at the Massachusetts Institute of Technology, Cambridge, has formulated a theory that can predict the patterns created when a viscous fluid falls onto a surface.

The authors modeled a thin thread of fluid landing onto a moving belt—a setup known as a fluid-mechanical sewing machine. They show that the system can be described by equations that depend on only a few “state” variables, such as the position where the jet hits the belt and the angle of the thread at that contact point. Like the thermodynamic state variables of a gas (temperature, pressure, or volume), these variables determine the present state of the system, as well as its future behavior. Depending on parameters like the height from which the fluid falls or the belt speed, the theory predicts that the system enters different phases, each of which corresponds to the formation of a specific configuration of loops and coils or, above a critical belt velocity, a straight line. The model successfully reproduces features observed in previously reported experiments. According to the authors, the theory could also be applicable to thin solid threads and might help guide the fabrication of patterned microstructures made of fiber or fabric.

This research is published in Physical Review Letters.

–Matteo Rini


More Features »


More Announcements »

Subject Areas

Fluid DynamicsInterdisciplinary Physics

Previous Synopsis

Related Articles

Viewpoint: Acoustic Experiments without Borders
Interdisciplinary Physics

Viewpoint: Acoustic Experiments without Borders

A new approach to laboratory acoustic experiments could remove unwanted effects caused by the reflections of acoustic waves from the boundaries of the experimental setup. Read More »

Synopsis: Beat Strong, My Liquid Gallium Heart
Fluid Dynamics

Synopsis: Beat Strong, My Liquid Gallium Heart

Applying a current across a drop of liquid gallium induces an oscillatory motion reminiscent of that of a beating heart. Read More »

Focus: Puzzling Tropical Wind Pattern Generated with Simple Model

Focus: Puzzling Tropical Wind Pattern Generated with Simple Model

2D simulations of the atmosphere, with few assumptions, can generate a slowly oscillating, tropical wind pattern that has puzzled atmospheric scientists. Read More »

More Articles