Polydisperse particle inline image method and its application onto gas–liquid flow in a stirred tank

Bubbles of different sizes exhibit distinct hydrodynamic behaviors and their dense coexistence complicates seriously the multiphase flow. The commonly‐used arithmetic average method (e.g., PIV) treats every bubble equally and consequently erases many physical details. In this study, a polydisperse particle inline image method is developed to simultaneously measure comprehensive feature set of every bubble in bubble swarms and carrier phase velocity. By harnessing the optimal frame rate capture alongside assigning IDs for tracking, complete identification of polydisperse swarm in single frame is integrated with the accurate acquisition of transient dynamics across multiple frames. In gas–liquid stirred tanks, the bubble deformation is notably intensified owing to the presence of collisions driven by velocity differences. A novel analysis of bubble hydrodynamics decomposed by bubble size reveals they are jointly commanded by the inertial effect and size effect. Actual flow regime of the system is essentially the superposition of multiple dissimilar flow patterns.