An Experimental Investigation of the Turbulent Kinetic Energy Budget within Sparse Organized Canopies

Sparse canopies are characterized by vegetative element spacing on the order of canopy height. Trellised agricultural systems are a common example sparse canopy. The flow field has characteristics of both typical homogenous canopy and rough wall boundary layer flows. The turbulent kinetic energy (TKE) balance was explored using high resolution stereoscopic particle image velocimetry (PIV) within a wind tunnel. These experiments were designed to explore the impact of both the row spacing and canopy element length scale. The row spacing was varied between 0.5 canopy height (H) and 2.7H to explore the transition from a homogenous to sparse canopy. Two canopy row designs were tested with different canopy element length scales while maintaining a constant optical porosity across all experiments. The results reinforce previous findings indicating TKE penetration deeper into the canopy with increasing row spacing. The specific components of the shear production and turbulent transport tensors give insights into the physical phenomena responsible for the structured turbulent observations.