Energy dissipation of flows in vegetated patches with spatially varying stem densit

To establish a compromise between ecological benefits and hydraulic flood risk, one needs a deep knowledge of fluid mechanics. In particular, and in what concerns energy loss, it is necessary to possess a good understanding of the processes that govern the rate of dissipation of TKE. This paper is aimed at quantifying this turbulent rate of dissipation in flows within arrays of emergent stems. To achieve that goal, experimental work was carried out featuring a periodic distribution of stem densities with minimum and maximum values of 400 and 1600 stems/m2, respectively. Instantaneous velocity maps were obtained with a Particle Image Velocimetry (PIV) system at several positions, comprehending vertical planes aligned with the flow direction and horizontal planes. Data is processed within the Double-Averaging Methodology (D-AM) in order to characterize the flow at the inter-stem scale. The dissipation rate of TKE is calculated and discussed as function of the macro scale Reynolds number and stem density. Mean flow energy loss is explained in terms of stem-scale processes.