On modeling Richtmyer-Meshkov turbulent mixing widths

We present several observations concerning the Richtmyer-Meshkov mixing widths after a shock or reshock passes through the interface between two fluids. The mixing evolves with two oppositely-moving fronts: A bubble (b) side into the heavier fluid and a spike (s) side into the lighter fluid. Our first observation concerns the reference surface used to partition the total mix width, h(b+s), into separate h(b) and h(s) widths. Next, we point out that if and when h(b) and h(s) obey power-laws t(theta) with separate theta(b) and theta(s), then h(b+s) cannot be given, except as an approximation, by a single theta(b+s). Finally, we describe a fully continuous model for h(i) (t), i = b, s, or b+s, as the solution to the drag equation with a time-dependent theta(i)(t). (C) 2019 Elsevier B.V. All rights reserved.