Zhang Jingzhou, Zhang Shengtang, Li Shufang, Yu Zicheng, Wang Wenjun, Zhao Wenhao, Li Guohao, Zhou Zheng
School of Water Conservancy and Hydroelectric Power, Hebei University of Engineering, Handan, China.
Hebei Key Laboratory of Smart Water Conservancy, Hebei University of Engineering, Handan, China.
Front Plant Sci. 2024 Oct 10;15:1424566. doi: 10.3389/fpls.2024.1424566. eCollection 2024.
The self-organizing biological characteristics of vegetation and human activities lead to the disruption of the continuous spatial attributes of natural watersheds, which are significant factors affecting river wetland ecosystems. To clarify the landscape ecological flow characteristics of vegetation patch distribution and fragmentation, this study used the three-dimensional Reynolds stress turbulence model in ANSYS Fluent software. The model considered three vegetation patch coverages under two different submersion states and four fragmentation types of vegetation patches under the same coverage conditions within specific vegetation areas. The flow characteristics of longitudinally discontinuous rigid vegetation patches, occupying half of the width of the river channel, were numerically simulated. The model's applicability was verified by indoor open-channel flume experiments. The results indicated that: (1) The streamwise velocity in vegetated areas is significantly lower than in non-vegetated areas, and the difference in flow capacity between vegetated and non-vegetated areas increases with patch coverage and fragmentation degree. (2) In the non-submerged state, the maximum Reynolds stress in the vegetated area is located at the bottom of the vegetation and is negatively correlated with patch coverage but positively correlated with fragmentation degree. In the submerged state, the maximum Reynolds stress is located near the top of the canopy and is positively correlated with both patch coverage and fragmentation degree. (3) The longitudinal turbulent kinetic energy in the vegetated area is significantly higher than in the non-vegetated area. In the non-submerged state, the turbulent kinetic energy in the vegetated area is negatively correlated with patch coverage but positively correlated with fragmentation degree. In the submerged state, the turbulent kinetic energy of the longitudinal distribution in the free layer of the vegetated area is positively correlated with patch coverage, negatively correlated with fragmentation degree, and is only reflected in the upstream vegetation area.
植被的自组织生物特性和人类活动导致自然流域连续空间属性的破坏，这些是影响河流湿地生态系统的重要因素。为了阐明植被斑块分布和破碎化的景观生态流特征，本研究使用了ANSYS Fluent软件中的三维雷诺应力湍流模型。该模型考虑了特定植被区域内两种不同淹没状态下的三种植被斑块覆盖率以及相同覆盖率条件下植被斑块的四种破碎化类型。对占据河道宽度一半的纵向不连续刚性植被斑块的水流特性进行了数值模拟。通过室内明渠水槽实验验证了该模型的适用性。结果表明：（1）植被区域内的流向速度明显低于非植被区域，植被区域和非植被区域之间的流量差异随着斑块覆盖率和破碎化程度的增加而增大。（2）在非淹没状态下，植被区域内的最大雷诺应力位于植被底部，与斑块覆盖率呈负相关，但与破碎化程度呈正相关。在淹没状态下，最大雷诺应力位于树冠顶部附近，与斑块覆盖率和破碎化程度均呈正相关。（3）植被区域内的纵向湍动能明显高于非植被区域。在非淹没状态下，植被区域内的湍动能与斑块覆盖率呈负相关，但与破碎化程度呈正相关。在淹没状态下，植被区域自由层纵向分布的湍动能与斑块覆盖率呈正相关，与破碎化程度呈负相关，且仅在植被区域上游体现。
