Characterization of gravity current formation for the use in detonation refraction experiments

Abstract

Detonation propagation through an interface is being studied at Caltech. In these experiments, the interface shape is determined by the gravity currents. This report presents an experimental study of the formation and the development of these gravity currents by an analog system in a water channel using water and salt water to simulate the density differences in detonation experiments. The major parameters such as the Reynolds number and the density difference were matched in both experiments to be able to compare the gravity current in the water channel and the gravity current in the Galcit detonation tube. In the present study, the gravity current was generated by the removal of a plate, and was visualized by adding food dye. The results confirm previous studies; Keulegan demonstrated in 1957 that the velocity of the gravity current is a function of the square root of the density difference. The interface is affect by the retracting of the plate which creates the wake effects. The Kelvin-Helmholtz instabilities on the upstream side of the gravity current create the visualized mixing zones. Finally, this study revealed how the gravity current interface into the Galcit detonation tube should develop and where the mixing zones should occur.