Turbulence structure and "Monami" phenomena in flexible vegetated open-channel flows
Turbulence structure and "Monami" phenomena in flexible vegetated open-channel flows
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DOI：
10.3826/jhr.2009.3536
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发表时间：
2009-01-01
影响因子：
2.3
通讯作者：
Nezu, Iehisa
中科院分区：
文献类型：
--
作者：
Okamoto, Taka-Aki;Nezu, Iehisa
天然河流水生植物是生态系统的重要组成部分。在有植被覆盖的明渠水流中，流速剖面在垂直方向上发生了很大的变化，导致了Kelvin-Helmholtz不稳定。因此，大规模的有组织的涡诱导，主导冠层之间的动量传递和标量浓度。相干涡旋的下游平流导致水生植被的相干波动，称为藻波。然而，在以往的研究中，流场可视化技术（如PIV）没有充分应用于这些复杂的流动，因此没有详细的信息之间的相互作用的流场和植物运动的存在。本文采用PIV和PTV相结合的方法，对具有柔性植被的明渠水流进行了湍流和植被运动的同步测量。本研究的前半部分主要研究藻奈美现象对平均流场和湍流结构的影响。后一部分研究了相干结构和植被运动之间的相互作用。
Aquatic plants in natural rivers are essentially important components of ecosystems. In vegetated canopy open-channel flow, velocity profiles are changed largely in the vertical direction resulting in the Kelvin-Helmholtz instability. Consequently, large-scale organized vortices are induced, which dominate the momentum transfer and scalar concentration among canopies. The downstream advection of coherent vortices causes the coherent waving of aquatic vegetation, referred to as Monami. However, the flow-visualization techniques such as PIV have not been sufficiently applied to these complicated flows in previous studies, such that no detailed information on the interaction between the flow field and the plant motion exists. Simultaneous measurements of turbulence and vegetation motion were conducted herein for open-channel flows with flexible vegetation by using a combination of PIV and PTV techniques. The former part of this study focuses on the effects of Monami phenomena on mean-flow and turbulence structures. The latter part examines an interaction between the coherent structure and the vegetation motion.