Fast Interface-Particle Interaction Simulations: the FIPI Project

The simulation of interfacial flows with particles that adhere to fluid interfaces has been recently subject of increasing interest. The large computational cost of current fully-resolved simulations for 3-phase flows with particles – LBMs or Immersed Boundary Methods require days of calculations on large computer clusters –  limits the ability to explore dynamics and collective effects with large number of particles and significant scale separation between the particle and the drop/bubble.


Figure 1: simulation of phase separation in the presence of surface-active particles

We have developed FIPI, a numerical method that enables to simulate O(10^3-10^4) particles interacting with fluid interfaces in just a few hours on a common PC. The computational efficiency of FIPI originates from the fact that particle-level phenomena such as the particle-interface interaction and hydrodynamic drag are modelled, while hydrodynamics and interfacial mechanics on scales much larger than the particle are fully resolved. We have shown that the code can capture accurately important effects such as the reduction of surface tension by repulsive particles.

Features of the current version of the code:

  • Particle inertia: treatment of inertialess and inertial particles
  • Particle-particle interaction: isotropic interaction potential, cohesive interactions with bond-bending resistance
  • Fluid solver: Stokes flow solver and finite-Reynolds number flow solver
  • Interface capturing: phase-field method
  • Boundary conditions: periodic
  • Multiphase features: liquid-liquid systems (variable density and viscosity included); liquid-gas systems not yet implemented
  • Can treat poly-dispersity in contact angle or particle size
  • Can treat particle embedded in the interface, particle desorption/adsorption and particles wettable by only one of the two liquids (e.g. to simulate completely hydrophobic particles in a oil-water mixture)
  • fast search for nearest neighbours in particle-interaction algorithm
  • programmed in C++ using modular programming (and a bit of OOP)

Code availability: I am happy to share the FIPI code with collaborators that can help develop the code further.

For more information, feel free to drop me a line at

Potential applications

  • particle-stabilised (Pickering) emulsions
  • particle-stabilised polymer blends
  • froth flotation
  • spray drying
  • spray scrubbing of particle-laden gases
  • colloidal drops


particlesonmetaldropletsFigure 2: ceramic particles on the surface of solidified liquid metal droplets (from: Li, Xinggang, et al. “Spray process modeling in metal matrix composite powder production.” Atomization and sprays 21.11, 2011)



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