Chapter 3: 2015 Problem 5: Two Balloons

In this work, we observed the different directions of air flow when two balloons are collected through preliminary experiments. We use phenomenological theory to describe the relation between pressure and elongation of balloons. A phase diagram is made according to the pressure and elongation relation from which the direction of air flow can be predicted. In experiment, we measured the pressure difference of balloons and plotted the pressure-elongation diagram to verify the theory. Besides, we take other factors that may influence the direction of air flow into account, like inflating history, Mullins effect, rubber material. Finally, we discuss the stability of equilibrium between two balloons.