NUMERICAL APPROACH FOR PREDICTING LAVA FLOW WITH OPENFOAM

The lava flow is one of the highly intriguing phenomena in fluid dynamics due to its complicated behaviour mostly determined by materials composition. One of the most important features is that the substances undergo stiffening and cooling caused by temperature variation, which changes the material property of the lava flow. While the portion of lava flow exposed to the atmosphere is gradually going into hardening but molten rocks below the surface are still very fluidic. For this reason, the lava flows inside the hardened surface usually travel farther. Due to its complicated phenomenon, experimental estimation of spatial extent of lava flow in the laboratory is very difficult, and instead, most studies have been carried out by using numerical approaches. In this study, an open source tool is employed to analyse the lava flow in the view of computational fluid dynamic. The computation was conducted using OpenFOAM-v2.4.0 with two-phase modelling for lava and the surrounding atmosphere. For two-phase flow, the momentum equation and the continuity are supplemented by transport equation (1) for volume fractions of the atmosphere and the lava flow. In order to consider the non-linearity of viscosity of the lava flow, Herschel-Bulkley or Bingham plastic fluid model is employed. In addition, the energy equation (2) is further included to consider the effect of temperature on the viscosity.