Seeing through the fluid dynamics of flexible vegetation and canopy turbulence

<p>Submerged aquatic vegetation within river and coastal environments alters the local flow hydraulics, in turn influencing sediment dynamics and bed morphology. Vegetation canopies complicate bottom topography, with flexible elements often invoking complex spatial variability. Acquisition of quantitative, long time-scale data concerning the fluid dynamics associated with flexible aquatic canopies has remained limited due to the physical and visual obstruction presented by vegetation.</p><p>The experimental based research detailed here implements a novel Refractive Index Matching (RIM) technique, combined with Particle Image Velocimetry (PIV), to acquire flow field measurements within, and above, a dynamically scaled surrogate flexible seagrass canopy. RIM provides an undistorted optical view through the vegetation canopies, facilitating the investigation of coherent flow structures and canopy dynamics at five different Reynolds numbers. A flexible vegetation canopy of length 1.4m, width 0.45m, and height 0.12m, occupied the entire width of the 2.5m long RIM flume facility at the University of Illinois. The flume was operated in a free surface mode with a flow depth of 0.36m. Results from a counterpart rigid canopy also offer comparability and broader application of these findings to a range of flow-biota environments. Transparent rods formed the rigid canopy, while the flexible canopy elements comprised of four thin polymer blades extending from a short rigid stem. Vegetation elements were placed in a staggered arrangement to form canopies with a density of 566 stems m<sup>2</sup>.</p><p>The results provide insights into canopy-based turbulence processes, including mixing layer properties associated with the canopy and vortex penetration. Deflection of the canopy and its waving motion is quantified, and linked to distinct hydrodynamic differences between the rigid and flexible canopies. Spatiotemporal variability associated with deflection of the flexible canopy, combined with the plant morphology, is shown to promote the spatial heterogeneity in turbulence distribution. Elucidation of instantaneous turbulent flow structures at various time intervals also reveals the links between above-canopy and in-canopy flow processes. This research provides new insights into the hydraulic processes of complex vegetated beds, including quantification of coherent flow structure evoultion. Application of these findings will help advance our knowledge of associated sediment transport dynamics, which is essential for interpreting larger-scale morphodynamic response and its role in environmental management.</p>

Numerical Study of Balancing between Indoor Building Energy and Outdoor Thermal Comfort with a Flexible Building Element

This study analyzed the environmental role of a flexible canopy as a microclimate modifier in balancing indoor energy demands and outdoor thermal comfort. Flexible building elements are often installed in traditional buildings, depending on the local climate in southern Europe. The architectural performance of a canopy was analyzed using several environmental software packages (Ecotect, Rayman, WinAir, DaySim, and EDSL TAS). Coupling methods were applied to determine the environmental influence of the attached building element, a canopy with fixed and operable panes in different orientations and locations. The results showed that the flexible canopy played a crucial role in reducing indoor energy demands (heating and electricity for lighting) and increasing outdoor thermal comfort under the canopy area. Outdoor thermally comfortable conditions ranging between 13 and 29 °C in the canopy space could be enhanced by 56.3% over the entire year by manipulating a flexible canopy, compared with a fixed canopy with 90% transparency in London. The flexible canopy with higher transparency helped increase outdoor thermal comfort in Glasgow, while one with lower transparency showed better performance during summer in London. The findings of this research will help broaden the range of architectural elements used in buildings.

Numerical simulation of fluid-structure interaction in the opening process of conical parachute

According to multi-node model, the dynamics equations of conical parachute system for simulating shape deformation process of the flexible canopy in the opening process were established. With the combination of dynamics equations code and computational fluid dynamics (CFD) software, the fluid-structure interaction investigation of the conical parachute was carried out. Also the change of parachute shape and flow field, inflation time, the rate of descent, the distance of descent, and other relevant data were achieved. This paper has focused on analysing vortex structure of the flow field in the opening process of conical parachute, and laid the foundation for studying mechanics mechanism of flow field variation of conical parachute in future.

Numerical simulation of fluid-structure interaction in the opening process of conical parachute

According to multi-node model, the dynamics equations of conical parachute system for simulating shape deformation process of the flexible canopy in the opening process were established. With the combination of dynamics equations code and computational fluid dynamics (CFD) software, the fluid-structure interaction investigation of the conical parachute was carried out. Also the change of parachute shape and flow field, inflation time, the rate of descent, the distance of descent, and other relevant data were achieved. This paper has focused on analysing vortex structure of the flow field in the opening process of conical parachute, and laid the foundation for studying mechanics mechanism of flow field variation of conical parachute in future.