Flow adjustment in the vicinity of a cylindrical canopy suspended in deep water

The time-averaged flow dynamics of a suspended cylindrical canopy patch with a bulk diameter of D is investigated using large-eddy simulations (LES). The patch consists of N_c constituent solid circular cylinders of height h and diameter d, mimicking patchy vegetation suspended in deep water (i.e. total water depth much larger than the canopy height). After validation against published data, LES of a uniform incident flow impinging on the canopy patch was conducted to study the effects of canopy density (0.16 ≤ ∅ = N_c(d/D)² ≤ 1, by varying N_c) and the bulk aspect ratio (0.25 ≤ AR = h/D ≤ 1, by varying h) on the near-wake structure and adjustment of flow pathways. The relationships between patch geometry, local flow bleeding (three-dimensional re-distribution of flow entering the patch) and global flow diversion (streamwise re-distribution of upstream undisturbed flow) are identified. The spatial extents of the wake, the flow diversion dynamics, and the bulk drag coefficients of the canopy patch jointly reveal the fundamental differences of flow responses between porous patches and their solid counterparts.