Abstract

I will describe two somewhat unrelated experiments with moving fluids. In the first experiment, an autocatalytic chemical reaction is used to generate rising plumes in a fluid under gravity. The reaction front is very thin, something like a flame front, and the reaction produces buoyancy both by releasing heat and by compositional change. The result is a self-stirred solution in which a small “flame bubble” evolves into a plume with a complex morphology. I will present both experiments and numerical simulations of the evolution of these plumes and “flame balls”. They have some resemblance to the initial stages of the deflagration of type Ia supernovae. The overall shape and subsequent rippling instability of icicles is an interesting free-boundary growth problem. It has been linked theoretically to similar phenomena in stalactites. We constructed a machine to grow icicles and determined their shape and the motion of their ripples. I will present time-lapse movies of slowly rotating, growing icicles. Rotation was added to encourage axisymmetry. I will discuss under what conditions the predicted ideal shape emerges and what we have learned so far about the ripples.