GRAVITY-INDUCED SEPARATION IN LIQUID FLAMES

We study the structure of a combustion wave propagating through a hete rogeneous powder mixture which initially forms a hard matrix. The matr ix is destroyed by the propagating combustion wave, due, e.g., to melt ing of some of the components of the mixture. Thus, a liquid bath is f ormed, in which processes such as heat and mass transfer as well as ch emical reactions determine the structure of the combustion wave, its p ropagation velocity and the composition of the reaction product. The l iquid bath is a suspension containing particles, either liquid or soli d, which may either be reactive or inert. Under the influence of gravi tational forces there is the possibility of relative motion of the ind ividual components of the mixture. This may result in separation of th e components under the influence of an external force field, such as g ravity, if the densities of the components differ from one another. Se paration is opposed by a friction force. To gain an understanding of t he phenomena associated with relative motion and separation during the propagation of the combustion wave, topics which heretofore have not been considered, we formulate and analyze a relatively simple mathemat ical model of ''liquid flame'' combustion in a gravitational force fie ld. We determine the structure of uniformly propagating combustion wav es and describe the possibility of multiplicity of such solutions. We also consider nonstationary waves and show that ''shock'' type solutio ns, with jumps in the composition of the sample, are possible.