17. Multiphase Flows with Viscoplastic Materials

Multiphase flows with viscoplastic materials are of paramount importance in many fields of science, being directly related to extremely important biomedical, environmental, and industrial situations. In the present work, two major multiphase flow scenarios involving viscoplastic materials are investigated: (1) the viscoplastic dripping; and (2) the bubble rising in a viscoplastic medium. In the former, we explore the breakup dynamics of a viscoplastic filament stretched by both gravity and surface tension. In the latter, we focus on the plastic effects that prevent an air bubble from moving via buoyancy in a viscoplastic medium. These problems are analysed by performing two-dimensional numerical simulations based on an adaptive variational multi-scale method for two materials (viscoplastic medium/air). The remarkable ability of the numerical framework in capturing complex multiphase systems with free surfaces is underlined by depicting the referred flow cases in the light of energy budget analyses, and scaling laws, thanks to which their physical mechanisms are stressed.