To initialize the spray for solid-cone injections, there are two options: use of an empirical nozzle discharge coefficient and use of a nozzle-flow model to determine nozzle discharge characteristics. These options are described in Nozzle Flow Model . Following this discussion are details on the Kelvin-Helmholtz / Rayleigh-Taylor droplet-breakup models in Kelvin-Helmholtz / Rayleigh-Taylor Breakup Model , and the unsteady gas-jet model in Unsteady Gas-Jet Model .