Turbulence characteristics around agricultural waste lagoons

Modeling gaseous emissions from open area sources requires assumptions concerning homogeneity and stationarity as well as spectral density so that Monin-Obukov and Kolmogorov theory can be applied. Are these assumption generally valid? Turbulence measurements were made using three dimensional (3D) sonic anemometers at 1.5 m, 4m and 16m heights above lagoon berms were made at nine farms over the past two years. A total of 2000 days of measurements have been collected over the study. Typical farm lagoons are at least partially imbedded in the farm buildings and treed surroundings. These configurations result in a wide range of upwind fetch conditions depending on wind direction. This study evaluates the homogeneity and stationarity for flow around the open sources for a number of obstruction and lagoon configurations assuming 15 min, 30 min, 45 min, and 60 min averaging intervals. Surprisingly the assumptions of stationarity and homogeneity near the surface appear to be valid for over 30-min intervals a wider range of conditions than might be expected.