Numerical simulation of particle encapsulation due to liquid thread breakup

The capillary instability of a liquid thread containing a periodic array of particles along the centerline is considered with reference to micro-encapsulation. The Navier–Stokes equation for axisymmetric flow inside and outside the thread is solved using an immersed boundary method implemented on a boundary-fitted orthogonal curvilinear grid that conforms with the particle shape. Numerical simulations are carried out to investigate the effect of the particle spacing, viscosity ratio, Reynolds number, and waveform of interfacial perturbations. The results show that fluid inertia delays the onset of the instability and may have an important effect on the number and volume of developing pure and encapsulating drops. The effect of the particle size diminishes as the Reynolds number is raised. An insoluble surfactant significantly delays the interfacial amplification and affects the process of thread breakup and the details of particle encapsulation. 2008 Elsevier Ltd. All rights reserved.