Japan Geoscience Union Meeting 2015

Presentation information


Symbol S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT35] Deep Earth science: Dynamics of plate, mantle, and core

Tue. May 26, 2015 6:15 PM - 7:30 PM Convention Hall (2F)

Convener:*Takashi Nakagawa(JAMSTEC/MAT), Shingo Watada(Ocean Hemisphere Research Center, Earthquake Research Institute, University of Tokyo), Takeshi Sakai(Geodynamics Research Center, Ehime University)

6:15 PM - 7:30 PM

[SIT35-P08] Implicit solution of the material transport of the core formation simulation

*Mikito FURUICHI1, Dave May2 (1.Japan Agency for Marine-Earth Science and Technology, 2.Institute of Geophysics, ETH Zurich)

Keywords:core formation, Stokes flow, free surface, implicit time integration, JFNK

In order to investigate the long time-scales of the global core formation process in a growing planet, we are developing the Stokes flow simulation code using MIC based techniques for material transport with a free-surface treatment. We are interested in the dynamical change of the internal structure after solidification of magma ponds/oceans during the core formation under a self-gravitating field, especially because it might lead to an initial heterogeneous structure in the deep mantle.
However current numerical solution method is difficult to solve the system coupled with the energy equation because the numerical system becomes stiff when the dynamical balancing time scale for the increasing/decreasing load by surface deformation is very short compared with the time scale associated with thermal convection. Any explicit time integration scheme will require very small time steps; otherwise, serious numerical oscillation (spurious solutions) will occur.
In this work, we propose to treat the advection as a coordinate nonlinearity, coupled to the momentum equation, thereby defining a fully implicit time integration scheme suitable for stiff problems [Furuichi and May, Compt. Phys. Commum 2015]. We utilize a Jacobian free Newton Krylov (JFNK) based Newton framework to solve the resulting nonlinear equations. We also investigate efficient solution strategies to reduce the computational cost to evaluate the nonlinearity on MIC advection.
These implicit methods are implemented within FD framework [Gerya and Yuen, 2003]. We examine the solution quality and efficiency of these methods by performing numerical experiments we have performed a series of numerical experiments which clarify the accuracy of solutions and trade-off between the computational cost associated with the nonlinear solver and time step size.