Surface wakes on ultra-soft solids

TL;DR

This paper investigates the surface wake patterns on ultra-soft solids caused by localized disturbances, revealing a new soft wake regime that connects fluid and solid surface wave physics through experiments and theory.

Contribution

It introduces a theoretical framework combining elastodynamics, capillarity, and gravity to explain surface wakes on ultra-soft solids, bridging fluid and solid wave theories.

Findings

Discovery of a steady V-shaped wake on ultra-soft solids.

Development of a generalized dispersion relation for soft surface waves.

Identification of a soft wake regime bridging fluid and solid surface wave physics.

Abstract

We explore the dynamical response of the free surface of an ultra-soft solid driven by a localized moving pressure disturbance. Experiments reveal a steady V-shaped wake analogous to a surface Mach wedge. A simple geometric argument provides a qualitative explanation consistent with observations. A theoretical framework combining elastodynamic, capillary, and gravitational effects yields a generalized dispersion relation that smoothly interpolates between Kelvin's theory of liquid interface wakes and Rayleigh's theory of elastic surface waves. Together, our experiments and theory reveal the existence of a soft wake regime that bridges fluid and solid surface wave physics, offering new routes for probing the dynamics of soft surfaces.