Thermomechanics of a drinking bird toy under radiative heating

A drinking duck is a traditional toy based on the principles of a heat engine. It operates by wetting the bird's head, causing evaporative cooling and condensation of the liquid inside the model, which rises and shifts the center of mass of the model. This process makes the duck tip and "drink," repeating the cycle until the water source is depleted. Here we experimentally study the drinking bird's dynamics in a setting where the thermodynamic cycle is modified, specifically by replacing the evaporative cooling of the head with radiative heating of the bottom of the toy using an infrared emitter. We develop a mathematical model combining concepts from physical damped pendulums with an evolving thermo-mechanical loading. We present comparisons between experiments and model predictions and discuss the crucial parameters including ambient conditions necessary to design the toy. This work might have utility in undergraduate education, combining key concepts of mechanical oscillators with non-equilibrium phase-change thermodynamics.