Multistable autonomous motion of fruit on a smooth hotplate

Area of Science:

• Physics
• Fluid Dynamics
• Materials Science

Background:

• Scale coupling phenomena require understanding multistability, involving shifts between stable states via unstable equilibria.
• Autonomous oscillations in objects on heated surfaces are influenced by fluid dynamics and material properties.

Purpose of the Study:

• To investigate the phenomenon of multistability and autonomous oscillation in corn cobs and various fruits on a heated surface.
• To elucidate the role of viscous lubrication, thermal effects, and fluid forces in driving object motion.

Main Methods:

• Observing autonomous oscillations (rolling, pitching, yawing) of corn cobs and six types of fruits on a glasstop hotplate.
• Analyzing the influence of buoyancy to inertia force ratio, lubricant film thickness, and temperature on motion dynamics.
• Investigating the role of cross products of orthogonal angular momentum and surface features in controlling motion.

Main Results:

• Corn cobs exhibited multistable autonomous oscillation, with viscous lubrication and transitional plumes.
• Six other fruit types displayed viscous wall-frictional multistability, primarily rolling and yawing.
• Object motion dynamics were linked to lubricant film thickness (h), tangential velocity (U), temperature (T), and mass (F).
• Plume vortex jets locked into the autonomous rolling cob oscillation, and surface fencing influenced motion drift.

Conclusions:

• Multistability is a key factor in understanding scale coupling, demonstrated by autonomous oscillations in various fruits.
• Fluid dynamics, including viscous forces and thermal gradients, significantly drive the observed autonomous motions.
• The study provides insights into the physics of self-propelled motion and surface interactions.