Hydrodynamics of core-collapse supernovae and their progenitors

Multi-dimensional fluid flow plays a paramount role in the explosions of massive stars as core-collapse supernovae. In recent years, three-dimensional (3D) simulations of these phenomena have matured significantly. Considerable progress has been made towards identifying the ingredients for shock revival by the neutrino-driven mechanism, and successful explosions have already been obtained in a number of self-consistent 3D models. These advances also bring new challenges, however. Prompted by a need for increased physical realism and meaningful model validation, supernova theory is now moving towards a more integrated view that connects multi-dimensional phenomena in the late convective burning stages prior to collapse, the explosion engine, and mixing instabilities in the supernova envelope. Here we review our current understanding of multi-D fluid flow in core-collapse supernovae and their progenitors. We start by outlining specific challenges faced by hydrodynamic simulations of core-collapse supernovae and of the late convective burning stages. We then discuss recent advances and open questions in theory and simulations.

SIMULATION OF FILTRATION AND CONVECTIVE BURNING IN BLOCK CHARGES OF POWDER GRAINS INHIBITED BY POLYVINYL BUTYRAL AT CONSTANT VOLUME

Increase of loading density could be considered as one of the ways of increasing muzzle velocity in guns. At the same time, reduction of maximum pressure requires increase in burning progressivity of the powder charge, which can be reached at the expense of coating of powder grains with polymer film and further compression to high density into block charge. Multidimensional numerical simulation of ignition and combustion of such charges is a relevant issue. Two-dimensional axisymmetric generalization of one-dimensional semianalytical model of convective burning of block charges is introduced. The gas-powder mixture is modeled by a two-phase nonequilibrium heterogeneous medium consisting of a multicomponent gas phase of the combustion products and a polydisperse condensed phase of the charge elements. Mathematical model and computational algorithm were validated through numerical simulation of the following problems: powder gas filtration in the dense charge, combustion of bulk and dense charges, consisting of 7-perforated grains, covered with film, in a closed vessel. Comparison of obtained results with experimental data demonstrates satisfactory predictive qualities of the model.