The Vertical Transports of Kinetic Energy by Turbulence and Pressure in the Boundary Layer

Abstract

The transport of energy by turbulence and pressure is examined for a turbulent surface layer over a dry prairie grassland. Both terms are found to be significant in the budget of turbulent kinetic energy. The values of the divergences are deduced by considering the variations of the non-dimensionalized terms with respect to z/L. It was found that the divergence of the turbulent kinetic energy flux was about equal to minus the buoyancy production. The main contribution was due to the divergence of the vertical transfer of the vertical component of kinetic energy. The divergence of pressure transfer was found to be of opposite sign and of about equal magnitude to the divergence of turbulent energy flux. The dissipation of turbulent kinetic energy about equalled the local production. The spectral components of the energy budget are briefly examined. It was found that the non-dimensional frequency range with no appreciable production nor dissipation was only about a decade wide whereas the spectral flux was constant to within 10% over about a two-decade band.