非恒定流下桩群绕流特性试验

非恒定流下圆柱绕流产生的尾涡会对结构疲劳损伤、水流挟沙能力等产生较大影响。本文基于非恒定流桩群绕流水槽试验，采用多普勒流速仪（Acoustic Doppler Velocimetry, ADV）测量了桩群周围的底层水流速度，分析了单峰洪水型非恒定流下，桩群绕流对底层流场、横纵向时均流速分布、横纵向紊动强度等的影响规律。研究表明：横、纵时均流速大小均与流量变化相关，纵向时均流速均为正值，横向时均流速在左右岸对称测点上大小一致。纵向流速相对紊动强度和横向流速紊动强度仅与流量大小有关，与流量所处的上升阶段与下降阶段无关，桩群绕流对附近流场的影响范围有限，且不同区域受到桩群绕流的影响程度存在一定差异。

Experiment on Flow Characteristics around Pile Group under Unsteady Flow

Under unsteady flow, the fatigue damage of the structure and the sediment carrying capacity of the water flow are greatly affected by the wake vortices generated by the flow around the cylinder. In this paper, based on the flume experiment of pile group around unsteady flow, the bottom flow velocity around the pile group is measured by Doppler velocimeter (ADV), and the influence and law of the flow around the pile group on the bottom flow field, transverse and longitudinal time average velocity distribution, transverse and longitudinal turbulence intensity are analyzed under the condition of single peak flood type unsteady flow. The research has shown that the average flow velocity in both horizontal and vertical directions is correlated with changes in flow rate. The average flow velocity in vertical direction is positive, and the average flow velocity in horizontal direction is consistent at symmetrical measuring points on the left and right banks. The relative turbulence intensity of longitudinal velocity and transverse velocity is only related to the magnitude of flow rate, and is not related to the rising and falling stages of flow rate. The influence range of pile group flow on the nearby flow field is limited, and there are certain differences in the degree of influence of pile group flow in different regions.