AbstractThe topic chosen for study as the Application Challenge is that of 2-dimensional buoyancy-opposed plane wall jet penetrating into a slowly moving, counter-current uniform flow. Buoyancy-influenced flows are commonly encountered in nuclear power plants, and these can present particular challenges both to modellers and to experimentalists. One example is found within the side-core region of the steel pressure vessel in magnox gas-cooled reactor systems. In this case, a downward-flowing wall jet of hot gas meets a slow upward flow of cool gas. The downward extent of the penetration of hot gas has a significant influence on the temperature distribution in the side-core region of the reactor pressure vessel.