Universal Characteristics in the Deepening Rate of Sheared Convective and Stable Boundary Layers

The deepening rate of a sheared turbulent fluid layer growing into a quiescent stably stratified layer is studied for cases where both the stress and the buoyancy flux are prescribed at the surface. Using DNS we systematically explore how the deepening rate depends on the initial stratification and on the value of the surface momentum and buoyancy flux. Situations with negative as well positive surface buoyancy fluxes are studied. Dimensional analysis shows how the various cases can be grouped into a single class that characterizes the situation. The simulations reveal a number of universal characteristics in the deepening rate of sheared convective and stable boundary layers. For several different class members we make a detailed study of the contributions to turbulence kinetic energy in order to determine the partitioning of shear production, dissipation and buoyancy production/destruction.