| Abstrakt: |
High-temperature melt spreading under a shallow water layer can lead to energetic interaction, known as the stratified steam explosion. One of the key uncertainties in the current understanding of this phenomenon is the mechanism for the formation of a premixed zone above the melt layer. It is known that the most energetic steam explosions occur when dispersed melt droplets are mixed with water in a certain proportion. There exists experimental evidence that high-temperature melt spreading is featured by intensive disturbances of the melt surface, visible as sporadic splashes to the height of about few centimeters. In this work, numerical simulations are performed on the interaction of a melt pool with water jets impinging on the free melt surface. Three phases are considered: melt, water, and vapor; the interfaces are modeled by the Volume of Fluid (VOF) method. Phase change is taken into account on the water-vapor interface. The problem is solved numerically in two- and three-dimensional framework. Firstly, impingement of a short-duration vertical water jet on the melt surface is studied, with the parametric analysis performed to establish the effect of the jet characteristics (mass, velocity, diameter) on the primary (due to development of a cavity on the melt surface) and secondary (central jet due to cavity collapse) splashes. Secondly, three-dimensional simulations are presented demonstrating the development of vapor film instability in an initially three-layered configuration (melt and water layers separated by a thin vapor film). Implication for the steam explosion problem is discussed. [ABSTRACT FROM AUTHOR] |
