Some Lagrangian Properties of Turbulence Deduced from Atmospheric Diffusion Experiments

Abstract

Selected Prairie Grass diffusion experiments have been analyzed to determine the so-called Hay-Pasquill scale factor relating Lagrangian and Eulerian scales of turbulence. It was found that an average value of the scale factor equal to four as suggested by Hay and Pasquill is obtained only under conditions closely approximating stationary processes. When experiments conducted under non-stationary as well as stationary conditions are considered, simple regression techniques are more efficient than the Hay-Pasquill technique for predicting the lateral spread of the diffusing plume. Lagrangian autocorrelations and eddy-wind variances for the crosswind velocity component deduced from the data using Taylor's diffusion equation are compared with corresponding Eulerian quantities for experiments conducted under thermally stable conditions. It is shown that the Lagrangian integral scale of turbulence exceeds the Eulerian scale and that the Lagrangian and Eulerian variances are approximately equal.