Modelling intrusions through quiescent and moving ambients

摘要: Volcanic eruptions commonly produce buoyant ash-laden plumes that rise through the stratified atmosphere. On reaching their level of neutral buoyancy, these cease rising and transition to horizontally spreading intrusions. Such intrusions occur widely in density-stratified fluid environments, this paper we develop a shallow-layer model governs motion. We couple dynamical for particle transport sedimentation, predict both time-dependent distribution ash within volcanic flux falls towards ground. In an otherwise quiescent atmosphere, spread axisymmetrically. find buoyancy-inertial scalings previously identified continuously supplied axisymmetric are not realised by solutions governing equations. By calculating asymptotic our show flow is self-similar, but instead only narrow region at front intrusion. This non-self-similar behaviour results radius intrusion growing with time t as t3/4, rather than t2/3 suggested previously. also identify drag-dominated flow, which described similarity solution radial growth now proportional t5/9. presence ambient wind, axisymmetric. Instead, they predominantly advected downstream, while same laterally thinning vertically due persistent buoyancy forces. close source, lateral regime, whereas far downwind, horizontal forces drive balanced drag. Our emphasise important role buoyancy-driven spreading, even large distances from formation flowing thin extensive layers form atmosphere result eruptions.