To grow or to shrink: A tale of two rubber balloons

TL;DR

This paper investigates the counterintuitive airflow between two connected balloons with different volumes, revealing how rubber elasticity influences whether air flows from larger to smaller or vice versa, and provides a comprehensive phase diagram of the phenomenon.

Contribution

It introduces a detailed analysis of airflow dynamics between balloons based on rubber elasticity, including a full phase diagram of flow behaviors.

Findings

Air flows from larger to smaller balloons under certain conditions.

Air can flow from smaller to larger balloons depending on elasticity and volume.

A complete phase diagram of airflow regimes is constructed.

Abstract

Two identical rubber balloons are partially inflated with air (to different extent) and connected by a hose with a valve. It is found that depending on balloon volumes, when the valve is opened the air will flow either from the larger (fuller) balloon to the smaller (emptier) balloon, or from the smaller balloon to the larger one. The phenomenon is explained in terms of the non-ideal rubber elasticity of balloons. The full phase diagram for the air flow dynamics is constructed.