The Clapping Book

TL;DR

This paper investigates the fluid-structure interaction in a book subjected to a steady airflow, revealing how aerodynamic forces induce self-sustained oscillations and clapping behavior through page lifting and bending dynamics.

Contribution

It introduces a physical model explaining the oscillatory clapping of a book caused by airflow-induced page lifting and bending, highlighting the role of aerodynamic forces and elastic resistance.

Findings

Pages lift off forming a bent stack due to aerodynamic forces.

Bending rigidity influences the oscillation cycle.

Self-sustained oscillations occur as the book claps shut repeatedly.

Abstract

A steady horizontal air stream flows across a book clamped at its downstream end. Pages lift off to form a growing bent stack whose shape is determined by the torques associated with aerodynamic forces, weight and elastic resistance to bending. As more pages lift off to join the bent stack, the increasing importance of bending rigidity to dynamic pressure eventually causes the book to clap shut. The process restarts, and self-sustained oscillations emerge. [Fluid dynamics video]