Damping of sound waves by bulk viscosity in reacting gases

TL;DR

This paper reexamines sound wave damping in reacting gases, revealing that chemical reaction damping occurs even when the bulk viscosity is zero, with a focus on recombining hydrogen plasma.

Contribution

It demonstrates that chemical reactions can cause sound wave damping independently of bulk viscosity, challenging previous assumptions.

Findings

Damping occurs despite zero bulk viscosity.

Recombining hydrogen plasma exhibits this damping behavior.

Challenges traditional views on viscosity and sound attenuation.

Abstract

The very long standing problem of sound waves propagation in fluids is reexamined. In particular, from the analysis of the wave damping in reacting gases following the work of Einsten \citep{Ein}, it is found that the damping due to the chemical reactions occurs nonetheless the second (bulk) viscosity introduced by Landau \& Lifshitz \citep{LL86} is zero. The simple but important case of a recombining Hydrogen plasma is examined.