Emulsion dynamics and equilibrium mechanisms during core formation

Portrait de Stephane Labrosse
Several mechanisms are possible for core formation among which metal rain in the magma ocean. This mechanism is important since it is often considered as the last event that allowed chemical equilibration between the core of the mantle. Decipherig this process from geochemical measurements requires a good understanding of the equilibrium mechanisms between the falling metal droplets and the surounding magma. I contributed to these issues with different colleagues using two independent approaches. 
Formation of a vortex ringWith Hiroki Ichikawa and Kei Kurita, we developped a numerical model of emulsion dynamics able to tackle interfacial tension. The numerical treatment is explained in Ichikawa and Labrosse (2010) and the application to magma ocean dynamics is discussed in Ichikawa et al (2010). The main interest of this approach is that it allows to compute self-consistently the distribution in sizes and velocities of droplets. A good agreement is found with standard scaling but allows to extend it toward the full distribution.
In Ulvrová et al (2011), we studied the equilibrium between a spherical droplet and the surrounding fluid by a combination of approximate analytical calculations and numerical simulations in different regimes. This allows to provide analytical expressions for the equlibration timescale in these different regimes.






Relevant publications

  1. Ulvrová, M., N. Coltice, Y. Ricard, S. Labrosse, F. Dubuffet, J. Velímský, and O. Šrámek (2011), Compositional and thermal equilibration of particles, drops, and diapirs in geophysical flows, Geochem. Geophys. Geosyst., 12, Q10014, doi:10.1029/2011GC003757.[AGU link] [PDF] [Details]
  2. H. Ichikawa, S. Labrosse & K. Kurita, Direct Numerical Simulation of an Iron Rain in the Magma Ocean, J. Geophys. Res.115, B01404, 2010. doi:10.1029/2009JB006427[PDF] [Details]
  3. H. Ichikawa & S. Labrosse, Smoothed particle approach for surface tension calculation in moving particle semi-implicit method, Fluid Dyn. Res., vol. 42, p. 035503, 2010. doi:10.1088/0169-5983/42/3/035503[Details]