Geometry and dynamics of passive scalar structures in compressible turbulent mixing

We present a structure-based numerical analysis of passive scalar mixing in decaying homogeneous isotropic turbulence (DHIT) and shock-turbulence interaction canonical configurations. The focuses on the temporal evolution ensembles structures, initialized as spheres different sizes relative to Taylor microscale. An algorithm is introduced track each individual structure interactions with other structures ensemble, relating changes surface geometry underlying physical processes (turbulent transport, dissipation, shock compression). tracking applied datasets from shock-capturing direct simulations DHIT, microscale Reynolds number Reλ=40 Mach Mt=0.2, STI cases which processed by wave at numbers M = 1.5 3.0. Temporal convolution increases for initially larger resulting higher probability locally hyperbolic geometries where breakup into smaller occurs. Shock-induced deformation amplifies processes, enhancing mixing, particularly structures. Mixing enhancement manifested an amplification surface-averaged gradient, alignment between gradient most extensional strain-rate eigendirection isosurfaces also across shock. Larger magnitudes its compressive correlate flatter regions. compression area coverage flat regions, localized.