EXPERIMENTAL STUDY OF OPEN CHANNEL FLOWS WITH TWO LAYERS VEGETATION



Tang, Xiaonan ORCID: 0000-0002-2434-9341, Wu, Shiqiang, Rahimi, Hamidreza, Xue, Wanyun and Lei, Yu
(2018) EXPERIMENTAL STUDY OF OPEN CHANNEL FLOWS WITH TWO LAYERS VEGETATION. In: The 2nd International Symposium on Hydraulic Modelling and Measuring Technology, 2018-5-31 - 2018-6-1, Nanjing, China.

[img] Text
Nanjing Conf_2nd Hydraulic Modelling_201806.pdf - Published Version

Download (1MB) | Preview

Abstract

Vegetation in river bed has a great impact on flow characteristics in rivers, especially during floods. Understanding the structure of flow in vegetated open channels, in both submerged and emergent conditions, would provide valuable scientific basis for evaluating the effect of vegetation on river flows. This paper studies the structure of the open channel flows with two layers vegetation through experiments. The experiments were conducted at Nanjing Hydraulic Research Institute (NHRI), in a 12 m long by 0.4 m wide straight flume with a rectangular cross-section at a constant slope of 0.004. The vegetation was modeled by dowels with 6.35 mm diameter at two different heights of 100 mm and 200 mm, which was configured with different patterns and placed over a 10 mm thick plate on the bed of the flume. The artificial vegetation covered a 7 m long portion of the flume. In our study, various flow depths were taken to cover both emergent and submerged flow conditions. The measurement locations have been chosen in certain key sections of the vegetation region such as free flow region, behind short and tall dowels. The experimental data showed that the velocity profile is mostly uniform over the depth in the both emergent and submerged cases, except location 1 (directly behind tall dowel) in a submerged condition. The flow velocity in the vegetation layer is significantly smaller than that in the surface layer (i.e. non-vegetation flow layer). A near-constant velocity dominates in the vegetation layer and increases close to the interface at the top of short vegetation. There is a sudden change in the shape of the velocity profile near the top edge of vegetation. The results also showed that the flow velocity is strongly dependent on measurement locations.

Item Type: Conference or Workshop Item (Unspecified)
Additional Information: https://www.iahr.org/index/event/16 http://ishmmt2018.iahr.org.cn/en
Uncontrolled Keywords: Vegetation, Submerged Vegetation, Emergent Vegetation, Two Layers Vegetation, Velocity Profil
Depositing User: Symplectic Admin
Date Deposited: 09 Feb 2021 08:27
Last Modified: 18 Jan 2023 23:00
URI: https://livrepository.liverpool.ac.uk/id/eprint/3115373