The Energy Budgets of the Turbulent Velocity Components and the Velocity-Pressure Gradient Interactions

Abstract

The kinetic energy budgets of the turbulent velocity components were examined for a turbulent surface boundary layer over a dry prairie grassland. The cospectra of the production terms were found to be similar to earlier studies. The main emphasis was placed on the longitudinal velocity-pressure gradient interaction term. It was found that the cospectra exhibited a double maximum shape. The small-scale maximum (scale size ?1.3 m) was not strongly dependent on either height or stability. The reasons for the lack of height dependence are not clear. A first approximation was made to the vertical velocity-pressure gradient interaction term and it was found that the spectral range was similar to that of the longitudinal velocity-pressure gradient interaction term. Because the velocity-pressure gradient terms were nonzero for values of f≈8, the onset of locally isotropic turbulence must be for higher values of f.