How do longitudinal waves propagate transversely?

TL;DR

This paper reveals and explains the physical phenomenon of longitudinal waves propagating transversely in elastic media, confirmed through simulations and analytical models, with implications for wave simulation accuracy and experimental sensitivity.

Contribution

It demonstrates that transverse propagation of longitudinal waves is a real physical effect, not a simulation artifact, and explores its interaction with objects and implications for wave analysis.

Findings

Transverse propagation of longitudinal waves confirmed as physical.

Transverse waves do not scatter when interacting with objects.

Behavior observed in shear and guided waves as well.

Abstract

Modern, high-fidelity numerical simulations have shown an apparently anomalous result: a longitudinal elastodynamic wave travelling perpendicular to the forcing direction. Numerical simulations, in combination with an analytical model, are used to confirm that this is not simply a simulation artefact, but a true physical phenomenon, as well as illustrating that the behaviour also occurs for shear and guided waves. When assessing how this unexpected wave interacts with objects, however, it is found that it does not scatter, despite being clearly measurable. This paper has uncovered and explained this behaviour, which is critical for the reliable use of numerical wave simulations in elastic media, as well as potentially for high sensitivity experiments and other polarised wave modalities.