An Assessment of the variation in Coefficient of Drag values for a thinned loblolly pine forest

Most Reynolds-Averaged Navier-Stokes (RANS)-based models for canopy flow perform reasonably well for dense vegetation. However, they consistently diverge from field-measured values when the vegetation is sparse. This occurs even when the Leaf Area Density is corrected for the thinner vegetation. One aspect of this model divergence is the Coefficient of Drag which is generally treated as a constant. This presentation will show the results of a study utilizing data from a loblolly pine forest near Winnfield, Louisiana. Field measurements of this forest were taken as the forest was progressively thinned. It is suspected that the Drag Coefficient must be adapted for dense and sparse vegetation. The results of a study involving the modification of the Drag Coefficient for a sparse canopy in a k-epsilon model will be presented.