Tracking and analysis of interfaces and flow structures in multiphase flows

Abstract

A methodology is introduced to study the dynamics of fluid interfaces in multiphase flows, emphasizing their break-up and coalescence. The algorithm tracks surfaces, here obtained by isocontouring an interface-describing scalar field (e.g., VOF) from a time series of volumetric snapshots. Physical and geometric information of the surfaces is used to find correspondences in a higher-dimensional space. Events are derived from found correspondences to describe the interactions among isosurfaces of closed fluid structures extracted at consecutive tracking time steps. The correspondences and events are filtered based on physical realizability, accounting for geometric constraints between consecutive time instances, as well as temporal constraints on the relations between surfaces in previous tracking steps. The resulting events are used to map the time evolution of all surfaces and their interactions into a graph, which is then queried to retrieve information on the dynamics of the fluid interfaces. The methodology is applied to a DNS dataset of droplet break-up in forced homogeneous isotropic turbulence (HIT). Emphasis is placed on the statistics of split and merge events, the lifetime of surfaces, and their geometric evolution in relation to the background flow fields.