Impact of gaps on the flow statistics in an emergent rigid canopy
Impact of gaps on the flow statistics in an emergent rigid canopy
复制标题
DOI：
10.1063/5.0088527
复制
发表时间：
2022-06
影响因子：
4.6
通讯作者：
Pallavi Ranjan;K. Mittal;L. Chamorro;R. Tinoco
中科院分区：
文献类型：
--
作者：
Pallavi Ranjan;K. Mittal;L. Chamorro;R. Tinoco
采用颗粒图像测速技术进行了高分辨率大涡流模拟和补充性实验室实验，对圆柱阵列间隙的流动响应进行了详细的定量评估。基础顶篷由密集的紧急刚性圆柱体组成，以规则的交错模式放置。间隔的长度从[公式：见正文]到24个不等，间隔为4 d，其中d为圆柱体的直径。在亚临界条件下使用弗劳德数[公式：见文]和体雷诺数[公式：见文]进行分析。结果表明，间隙会影响冠层上游和下游邻近区域的流量统计。平均流量影响区域为[公式：见文]，二阶统计量影响区域为[公式：见文]。林隙内无因次时均流速随林隙间距变化不大；然而，面内湍流动能k从间隙开始与[公式：见文]处归一化后呈现出一致的衰减率。在实际应用中，应急冠层作为一种被动的间隙流湍流发生器。k的流向依赖性在[公式：见文本]内遵循指数趋势，并在[公式：见文本]处过渡到幂律。与冠层内的k相比，间隙内k的最大值明显较低，这证明了代表冠层流量统计的间隙测量的局限性。我们提出了一个基本框架，用于从间隙测量中估计具有代表性的冠层内统计数据。
High-resolution large eddy simulations and complementary laboratory experiments using particle image velocimetry were performed to provide a detailed quantitative assessment of flow response to gaps in cylinder arrays. The base canopy consists of a dense array of emergent rigid cylinders placed in a regular staggered pattern. The gaps varied in length from [Formula: see text] to 24, in intervals of 4 d, where d is the diameter of the cylinders. The analysis was performed under subcritical conditions with Froude numbers [Formula: see text] and bulk Reynolds numbers [Formula: see text]. Results show that the gaps affect the flow statistics at the upstream and downstream proximity of the canopy. The affected zone was [Formula: see text] for the mean flow and [Formula: see text] for the second-order statistics. Dimensionless time-averaged streamwise velocity within the gap exhibited minor variability with gap spacing; however, in-plane turbulent kinetic energy, k, showed a consistent decay rate when normalized with that at [Formula: see text] from the beginning of the gap. The emergent canopy acts as a passive turbulence generator for the gap flow for practical purposes. The streamwise dependence of k follows an exponential trend within [Formula: see text] and transitions to a power-law at [Formula: see text]. The substantially lower maximum values of k within the gap compared to k within the canopy evidence a limitation of gap measurements representative of canopy flow statistics. We present a base framework for estimating representative in-canopy statistics from measurements in the gap.