Fingering Instability in Filtration Combustion

Faculty:  Chris Wahle

Summary:

The so-called fingering phenomenon in filtration combustion resembles that of the Saffman-Taylor problem which was originally formulated to describe the displacement of one fluid by another having a smaller viscosity.  Fingering in filtration combustion is an instability of planar combustion waves, in which the combustion front assumes the form of a finger, or multiple fingers, and propagates through the interior of a porous sample of combustible particles.  This phenomenon has been observed in experiments, but little theory has been developed to provide explanations of the experiments.  Fingering combustion presents a danger in the context of smoldering, since burning occurs inside the sample and not on its surface.  Thus, unwanted burning is hidden from view and may go unnoticed for a longer period of time. Fingering phenomena is a complicated subject area which is described in no less than two dimensions.  Experiments reveal intricate pattern formation along the interface between the fresh unburned fuel and the combustion products.  The purpose of the research is to gain a better understanding and shed new light on the observed phenomena.