Simulations and models for the Richtmyer-Meshkov instability with broadband perturbations

The Richtmyer-Meshkov instability (RMI) is shock driven and affects many phenomena from inertial fusion to supernova explosions. The behavior of single-modes in the RMI has been studied extensively but less is known with the broadband perturbations that occur in applications. Here, we describe extensive numerical simulations and modeling of the RMI with broadband perturbations with an initial power spectrum of the form P proportional to k(m), where k is the wavenumber. The hydrodynamic condition is the same as in the theta-Group Collaboration [Thornber et al., "Late-time growth rate, mixing, and anisotropy in the multimode narrowband Richtmyer-Meshkov instability: The theta-group collaboration," Phys. Fluids 29, 105107 (2017)] with a Mach similar to 1.86 shock and gamma-law = 5/3 fluids with Atwood number A = -0.5. The bubble amplitude h(B) is found to grow in two stages. Initially, h(B) undergoes a phase-inversion and grows linearly in time (t) at a rate consistent with a linear theory. Asymptotically, h(B) grows as a power law similar to t(theta) when k|h(B)| > O(1), where k is the average wavenumber for the initial spectrum. The RMI behavior in simulations and modeling agree over a wide range of exponent m, spectral width, initial amplitude, and time. The agreement is quantified objectively using statistical analysis.