Local and Nonlocal Impacts of Gaps on Submerged Canopy Flow. Issue 2 (4th February 2021)

• Record Type: Journal Article
• Authors: Chung, Hayoon; Mandel, Tracy; Zarama, Francisco; Koseff, Jeffrey R.
• Is Part Of: Water resources research. Volume 57:Issue 2(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-04
• Subjects: canopy -- gaps -- Kelvin‐Helmholtz -- submerged aquatic vegetation -- patch -- turbulence; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2019WR026915
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Although shear layers generated by submerged vegetation reach a steady state once production and dissipation are balanced within a canopy, shear layers found in gaps and after trailing edges of canopy patches are inherently different and thereby perturb the canopy's mean and turbulent fields. Experiments were conducted in a laboratory flume to study canopy systems in which two model patches of submerged, rigid cylinder arrays are interrupted by a gap of varying stream‐wise lengths. Results show that, consistent with past studies, gaps locally enhance turbulence. However, this perturbation does not remain "local" within the gap, instead introducing enhanced turbulent energies throughout the water column that are transported downstream and thereby perturb the canopy flow. The study suggests a scaling, E = H − h c q U 2 L 2, which compares the eddy turnover time of the turbulence produced by the gap to the advection time downstream the second patch, that can be used to predict if turbulence perturbations induced by an upstream gap will influence the turbulence at a given distance downstream. Key Points: Different lengths of canopy patches, if shorter than for fully developed canopy flow, introduce varying levels of turbulence to its wake Gaps locally enhance and redistribute turbulence throughout the water column The length of the gap has the greatest influence on the level of turbulence and flow disturbance to the downstream canopy patch Turbulence enhancements formed locally within gaps disrupt canopy flows by transporting and propagating downstream to nonlocally enhance turbulence