基于粒子图像测速技术的淹没植被斑时均尾流结构研究

水生植被对维持生态系统健康稳定具有重要意义,而绕有限尺寸淹没植被群落的流动又对物质输移和植被演化具有重要影响。本研究将淹没植被群落概化为圆形刚性圆柱阵列,并基于实验室水槽实验,采用粒子图像测速技术对不同密度植被群落的尾流时均流场进行测量,以探究植被密度变化对其尾流结构的影响。结果表明：植被斑内的顺流向出流强度随植被密度的增大而增大,同时植被斑直径的大小也对出流强度有影响;当植被密度大于0.1时,植被斑的群体行为变得十分明显,在时均流场中植被斑下游会产生类似于淹没实心圆柱的三维“拱”形回流涡,其与植被斑之间的距离随植被密度的增大而减小;稳定尾流区长度与拱形涡到植被斑后缘的距离成近似正线性相关关系。研究成果对深入理解植被群落的绕流结构具有促进意义。

Investigation of the mean wake structures of submerged vegetation patches based on PIV measurement

The flow around submerged vegetation patches plays a critical role in material transportation and vegetation evolution. This study used particle image velocimetry to investigate the effects of array density on mean wakes of submerged vegetation patches modeled as circular rigid cylinder arrays, based on laboratory flume experiments. The results showed that the streamwise bleeding flow decreased as the array became denser, and was also affected by the patches'' diameters. When the array density was larger than 0.1, the group behavior of the array became significant and a symmetric "arch" vortex was formed behind the array, similar to a submerged solid cylinder, and moved closer to the array with increasing array density. The length of the steady wake region was approximately linearly correlated with the distance from the arch vortex to the array. This study is of great significance for further understanding the flow structures around vegetation patches.