Transient stratification force on particles crossing a density interface

Lilly Verso, Maarten van Reeuwijk, Alexander Liberzon

Research output: Contribution to journalArticlepeer-review


We perform a series of experiments to measure Lagrangian trajectories of settling and rising particles as they traverse a density interface of thickness h using an index-matched water-salt-ethanol solution. The experiments confirm the substantial deceleration that particles experience as a result of the additional force exerted on the particle due to the sudden change in density. This stratification force is calculated from the measurement data for all particle trajectories. In absence of suitable parameterisations in the literature, a simple phenomenological model is developed which relies on parameterisations of the effective wake volume and recovery time scale. The model accurately predicts the particle trajectories obtained in our experiments and those of Srdić-Mitrović et al. (1999). Furthermore, the model demonstrates that the problem depends on four key parameters, namely the entrance Reynolds number Re1, entrance Froude number Fr, particle to fluid density ratio ρpf, and relative interface thickness h/a.

Original languageEnglish
Article number103109
JournalInternational Journal of Multiphase Flow
StatePublished - Dec 2019


  • 3D-PTV
  • Density interface
  • Inertial particles
  • Lagrangian trajectories
  • Stratification force


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