Numerical simulation of turbulent exchange flow in aquatic canopies

Laboratory Studies on Nearshore Density-Driven Exchange Flow over a Partly Vegetated Slope

“…By rapidly lifting up the partition, gravity currents were produced down the slope. After the data was collected, a binary image thresholding technique was applied to delineate the current boundary [20,32]. The colored images were firstly converted to binary pictures by using the commercial software Matlab.…”

“…Consequently, the volumetric discharge rate per unit width = dV dt should also be a function of time t and tank slope S 0 . When the gravity currents flow over a flat bottom with the model canopy distributed on only one side and h d is assumed constant, L v , V and q can be analytically expressed as [20]:…”

“…Coates and Ferris [19] revealed that shading from floating plants could generate exchange flows that are displaced downward due to the roots. In contrast, the inherently resistant forces of rooted vegetation significantly reduce current speed and volumetric exchange flowrates while increasing flushing time [8,20]. Tanino et al [5], Zhang and Nepf [8] and Zhang and Nepf [20] modeled vegetative drag using a very common quadratic law.…”

“…In contrast, the inherently resistant forces of rooted vegetation significantly reduce current speed and volumetric exchange flowrates while increasing flushing time [8,20]. Tanino et al [5], Zhang and Nepf [8] and Zhang and Nepf [20] modeled vegetative drag using a very common quadratic law. Zhang and Nepf [5] investigated the combined effects of shading and drag from emergent and rooted vegetation on thermally driven flow over a flat bed and reported that the exchange flow was inertia-dominated in the initial stage and rapidly transitioned to being drag-dominated.…”

“…In contrast to the work of Ho and Lin [25], this new configuration (a model canopy on one side and open water on the other) can better simulate real field conditions, where an exchange flow is more likely to be produced by vegetation shading. As stated by Zhang and Nepf [20], although the experiment is a simplification of the field situation in which the difference in density varies over the course of the diurnal heating process, the setup and transient time scale for the exchange flow is short compared with the time scale of the diurnal temperature variations. Thus, the results from these simplified experiments are reasonable and applicable for evaluating the scales of the speeds and exchange flow rates of the current.…”