Recent developments in second-moment closure for buoyancy-affected flows

The paper summarizes a new type of second-moment closure, more elaborate in form than earlier versions but designed to satisfy the two-component limit to which turbulence reduces at a wall or at a sharp density interface. Because they are intrinsically realizable, closures of this type are believed to offer the prospects of a wider range of applicability than earlier schemes. They may also be expected to display better numerical stability. Several illustrative applications are provided including the downward directed warm jet, the stratified mixing layer and buoyancy affected grid-turbulence decay. Extension of the scheme to near wall flows appears possible without introducing empirical 'wall-reflection' terms, at least in flows parallel to walls.