Flow Field Characteristics at the Spanwise Edge of a Vegetative Canopy Model

• Published in: Boundary-layer meteorology Vol. 190; no. 10; p. 40
• Main Authors: Winiarska, Ewelina, Liberzon, Dan, van Hout, René
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.10.2024; Springer Nature B.V
• Subjects: Atmospheric boundary layer; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Canopies; Canopy; Desertification; Dominance; Dynamic structural analysis; Earth and Environmental Science; Earth Sciences; Energy transport; Flow characteristics; Flow structures; Fluid dynamics; Gradients; Image contrast; Interfaces; Internal layout; Kinetic energy; Meteorology; Particle image velocimetry; Plant cover; Research Article; Reynolds stress; Reynolds stresses; Swirling; Transport equations; Transport processes; Turbulent flow; Turbulent kinetic energy; Velocity; Velocity measurement; Vorticity; Particle image velocimetry; Spanwise canopy edge; Instantaneous interface characteristics; Turbulent canopy flows
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1007/s10546-024-00881-x

This study investigates the complex flow field across a spanwise vegetative model canopy edge focusing on turbulent transport processes. Utilizing stereoscopic particle image velocimetry, the three velocity components were measured in wall-parallel planes at various elevations within canopy across the spanwise canopy edge. Conventional ensemble averaged results were contrasted with those obtained by conditionally averaged flow properties across instantaneous internal interfaces in the flow to understand their contribution to the ensemble average. The conditional average captured the strong gradients in mean velocities, Reynolds stresses, vorticity, swirling strength, and turbulent kinetic energy production across the dynamically changing instantaneous interface. In contrast, the conventional ensemble average smeared out the strong gradients. Small magnitudes of advective terms in the turbulent kinetic energy transport equation suggested weak secondary transverse flows in the present model canopy. The turbulent flow structure across the spanwise canopy edge was further investigated using Quadrant-Hole analysis for both averaging approaches. Conventional ensemble averaged results indicated a shift from sweep to ejection dominance when moving from canopy into the open patch, while the conditional average showed only sweep dominated transport. In contrast to a homogeneous canopy layout, below canopy height at the canopy edge, sweeps and ejections lose their dominance in vertical turbulent transport. The present results show that the dynamics of internal interfaces govern the ensemble averaged results and a possible implementation into existing models is proposed. The present results are expected to increase understanding of spanwise turbulent transport and aid in developing strategies to mitigate desertification.