EFFECTS OF SECONDARY FLOWS ON THE CONTAINMENT OF A HEAVY GAS IN A VORTEX

Abstract : Binary diffusion in confined vortices (of the type considered for hydrodynamic containment in a gas-core nuclear rocket) is investigated theoretically and experimentally. An approximate integral solution is presented for the species distribution resulting from the actions of convection, and concentration and pressure diffusion. The flow model includes secondary flows induced by boundary-layer interaction on the end walls of the vortex chamber. The qualitative effect of varying the degree of boundary-layer interaction is demonstrated by a flow-visualization experiment using dye in a water vortex. Quantitative data are obtained from an experiment in which iodine vapor and heated helium are premixed and injected tangentially into a vortex chamber, forming a lowdensity, high-velocity flow field. The resulting radial distribution of iodine concentration is determined optically. Peak density ratios of iodine to helium within the vortex are found to be as much as three times the density ratio of the mixture flowing into the chamber. The experimental data agree favorably with the theoretical predictions and demonstrate that a gas of high molecular weight can be substantially retained in a vortex comprised of a gas of low molecular weight. (Author)