Unfolding The Link between Forest Canopy Structure and Flow Morphology

Turbulent flows over horizontally homogenous rough surfaces have long been studied, and they are categorized as rough-wall boundary layer flows. On the other hand, flows over homogeneously distributed bluff elements (e.g., homogenous forests) are typically described through a mix of rough-wall boundary layer and mixing-layer theory. However, most vegetated canopies are not homogenously distributed but instead are plagued with gaps and spatial heterogeneities of different scales. In these cases, it still remains unclear what the dominant flow traits are and how spatial heterogeneity affects them. Therefore, this project aims to characterize flows over vegetated canopies with scales of spatial heterogeneity ~ Ο (<span style="font-size:10.8333px">10²) m, with a uniform under-canopy roughness and neutral stratification.

Large Eddy Simulations of the atmospheric boundary layer with varying geostrophic forcing are used. The vegetated canopy morphology is described through the metric of Lacunarity, an index that is then used to investigate non-dimensional relationships between canopy morphology and turbulence statistics. Preliminary results illustrate a progressive transition from rough-wall boundary layer flow characteristics to those of a mixing layer with increasing lacunarity.