Abstract
AbstractTo simulate a glacial lake outburst flood, we employ a comprehensive physically based general two-phase mass flow model (Pudasaini, 2012). This model accounts for a strong interaction between the solid and fluid phases and incorporates buoyancy and other dominant physical aspects of the mass flows such as enhanced non-Newtonian viscous stress, virtual mass force and generalized drag. Our real two-phase mass flow simulation describes explicit evolution of the solid and fluid phases and the debris bulk as a whole, akin to torrential debris flows or debris floods during glacial lake outburst floods (GLOFs). The emptying of a lake following rapid collapse of a restraining dam, the consequent downslope motion of a mixed solid–fluid mass, and the tendency of the mass to form extruding plumes are analyzed in detail for different flow configurations, volumes, conduit geometries and boundary conditions. The solid and fluid phases evolve completely differently and reveal fundamentally different dynamical behaviours. During the flow, the relatively long fluid tail follows the solid-rich dense frontal surge head. The bulk debris develops into a frontal and side levee as derived from the initial frontal moraine dam. Results show that our high-resolution, unified simulation strategies and the advanced model equations can be applied to study the flow dynamics of a wide range of geophysical mass flows such as snow and rock–ice avalanches, debris flows and flash floods as well as GLOFs. This may help substantially in forming a basis for appropriate mitigation measures against potential natural hazards in high mountain slopes and valleys.
Highlights
Mass wasting and mass flows are very important phenomena in process industries and geophysical events
We analyze in detail the influence of initial channel geometry, material volume and boundary conditions on the initial stages of the outburst floods and the subsequent dynamic evolution of glacial lake outburst floods (GLOFs)
In order to simulate a GLOF, we have presented simulation results for two-phase mass flows down an inclined channel that allows the material to flow in a conduit and to spread both downslope and across-slope
Summary
Mass wasting and mass flows are very important phenomena in process industries and geophysical events. Physical aspects of flow: (1) enhanced non-Newtonian viscous stress induced by changes in the volume fraction of solid; (2) virtual mass; and (3) generalized drag (Pudasaini, 2012). This model constitutes the most generalized twophase avalanche and debris flow model to date. We present some novel and basic geometrically 3-D simulation results for flows of a real two-phase debris material down an inclined channel describing a rapidly cascading GLOF or a mountain tsunami This includes different initial flow configurations, volumes, channel geometries and boundary conditions. For a mechanically enhanced approach to the modelling of rock–ice avalanches, we refer to Pudasaini and Krautblatter (2014), where the mass and momentum exchanges of the phases are considered
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