Fluid Dynamics of High Pressure Volcanic Eruptions
ProQuest, 2008 - 115 pages
In large explosive volcanic eruptions, the eruptive fluid issues from the vent as a high speed, compressible gas with entrained solid particulates. It is important to quantify the behavior of this gas-thrust region because it provides a connection between the fluid dynamics in volcanic conduits with those of the buoyant column. If the eruptive fluid velocity is at or greater than sonic and vent pressure is higher than atmospheric pressure, the dynamics will be complicated by the presence of standing shock waves that can drastically alter the distribution of the vertical heat flux necessary for eruption column stability. Although application of compressible jet dynamics to explosive volcanic eruptions was first suggested over 25 years ago by Kieffer (1981), the concept has yet to be widely applied in modeling and analysis of explosive eruption columns. Here I present results from computational simulations of high pressure volcanic eruptions. I show that the dynamics resulting from high pressure volcanic vents can have a large influence on the downstream dynamics of the eruption column. The effects of standing shock waves may change the stability of the column and lead to the formation of pyroclastic flows.
Numerical Methods and Benchmarking
Expansion Dynamics of Overpressured Volcanic Jets
Effects of Vent Overpressure on Eruption Column Stability
3D simulation analytical annular velocity profile annulus atmospheric pressure axis benchmarking buoyant plume CFDLib Chapter decompression decrease downstream effects of vent equation eruption column eruptive fluid Figure flow field fluid dynamics free-slip gas-thrust region grid cells heat flow heat flux distribution heat flux profile high pressure ID models increase inflow boundary Kieffer and Sturtevant laboratory experiments Ladenburg Lewis and Carlson Mach disk height Mach number magma mass flow mesh mesh scaling momentum multiphase Neri nozzle outflow boundaries overpressure ratio overpressured jets overpressured simulations overpressured volcanic jet peak vertical heat plume dynamics plume radius predicted pressure balanced jets pyroclastic flows qpeak radii rvent shear layer shock structures simulation with vent snapshots sonic sound speed standing shock waves stratified atmosphere supersonic temperature underexpanded jets vent conditions vent exit vent overpressure vent pressure vent radius vertical heat flux vertical velocity volcanic eruptions volcanic plumes Woods and Bower