Bridging the local and the global: a physically constrained buoyancy--drag model for unified prediction of Rayleigh--Taylor and Richtmyer--Meshkov mixing widths across density ratios

Accurate prediction of the macroscopic width of Rayleigh--Taylor (RT) and Richtmyer--Meshkov (RM) turbulent mixing layers is central to inertial confinement fusion and supernova dynamics. However, bubble--spike asymmetry, density-ratio dependence and unsteady forcing pose a persistent closure challe