Principles and performance of TCL-based second-moment closures

The paper argues that to achieve the desired width of applicability for use in general CFD software turbulence modelling at second-moment level needs to be based upon making the pressure-strain term and other major processes comply with the two-component limit (TCL), a strategy first advocated by Lumley [24]. The approach is especially powerful for flows close to surfaces that are far from flat and in applications to horizontal, stably-stratified flows where, due to the action of buoyancy, the stress tensor also approaches a two-component form. A range of recent applications of TCL modelling is presented including flow in curved ducts, three-dimensional wall jets, free-surface jets and stably-stratified mixing regions.