IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
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You are here : eLibrary : IAHR World Congress Proceedings : 35th IAHR Congress - Chengdu (2013) : THEME 4 - HYDRO-ENVIRONMENT : Impact of Tree Scale on Drag: Experiments in a Towing tank
Impact of Tree Scale on Drag: Experiments in a Towing tank
Author : Johanna Jalonen and Juha J„rvel„
Reliable estimation of vegetative flow resistance calls for physically sound and readily measurable parameters describing woody vegetation. For these purposes, many researchers have investigated hydraulic resistance of vegetation in flumes with living and artificial plants. However, due to the restrictions of flume size the experiments are often conducted with parts of trees. Consequently, it is n ot clear how the scale affects the hydraulic resistance. We investigated the vegetative drag for 4 common tree species of different lengths (0.9?3.4 m) in a towing tank. The drag forces were directly measured both in leafy and leafless conditions at the velocity range of 0.1?1.5 and 0.1?2.5 m\s, respectively. Frontal and side projected areas were recorded during the measurements using submerged video cameras. For all specimens, biomass, projected area in still air, and one-sided leaf area were determined. The results indicated that the sum of stem and leaf areas was a suitable resistance estimate independent of the tree length. In contrast, the dry mass and volume were not adequate drag predictors, as distinct differences were found for the smaller specimens compared to the taller ones. The results further suggested that significant reconfiguration of the leaves took place by 0.5 m\s, as the share of leaf drag to the total drag decreased significantly at the lowest velocities and remained almost constant for velocities above 0.6 m\s.
File Size : 446,569 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 35th IAHR Congress - Chengdu (2013)
Date Published : 18/07/2016
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