Cooling of Pyroclastic Density Currents from an Explosive Eruption

Tungurahua volcano is one of the most active volcanoes in Ecuador and is located approximately 120 km south of Quito. It has been active since 1999 and in 2006 Tungurahua had a vigorous episode that produced 51 pyroclastic density currents (PDCs). It is important to use verified numerical models to study the thermal history of PDCs and the clasts within them because it provides important details about the fluid dynamics of the flow. Generally, the cooling rate of the flow will depend on the particle concentration, the entrainment rate of ambient air, and the entrainment of eroded substrate. The thermal history of the flows also depends on the particles’ rate of heat transfer or conduction. We model the conduction of a spherical particle with a varying heat flux boundary that is modeled using the Ranz-Marshall correlation. We add the heat conduction model of a sphere into a numerical model that uses the Eulerian-Eulerian-Lagrangian [EEL] approach to look at how the particle moves and interacts with the surrounding gas, temperature, topography, and adjust the parameters to see how the particle cools with time and subsequently how the flow cools with time. The goal is to eventually create a model of the fluid dynamics and thermal history of the entire flow and obtain the depositional temperatures. The multiphase model using the EEL approach and the field data collection will enable one to examine the in-situ responses between the speed at the front of the flow, how well the flow mixes and the cooling of clasts. This will provide information on air entrainment. Air entrainment influences the final run-out distance of the flow, which is important to study because of the hazards associated with volcanic eruptions and pyroclastic density currents.