Rayleigh-Taylor Instability in Elastic-Plastic Materials

The Rayleigh-Taylor instability is investigated in a material with a shear modulus $\ensuremath{\mu}$ and yield stress ${\ensuremath{\sigma}}_{0}$. Incompressible experiments are conducted with constant and impulsive acceleration histories $g(t)$ using a fully characterized material. Two dimensional (2D) perturbations are found to be stabilized for wave number $k>\ensuremath{\rho}g/2\ensuremath{\mu}$ and initial amplitude ${h}_{0}<{\ensuremath{\sigma}}_{0}/\ensuremath{\rho}g$, where $\ensuremath{\rho}$ is the density. The stability region is larger for 3D perturbations. Unstable modes are found to grow classically during the acceleration phase, but they can recover elastically while coasting.