Three-dimensional velocities induced by wind and ship activity in the near-bottom regions of Lake Taihu

The three-dimensional current velocities (u1, u2, and w) in the lower and upper layers at the monitoring point were measured using a Nortek ADV, with a sampling frequency of 100 Hz. ADV was positioned 5 cm above the lakebed, and mounted on a bottom-mounted holder, facing downward. In this research, the horizontal flow was redistributed into the main stream u1 (x-direction) and the transverse flow u2 (y-direction), based on statistical analysis. The vertical velocity, w, represented flow in the z-direction, with upward movement considered positive. The field survey aimed to discern disparities between wind- and ship-induced disturbances. Data measured under wind influence were collected on July 26, 2018, with wind speeds ranging from 0 to 11 m/s. On July 27, 2018, we conducted 12 different shipping experiments. The shipping scenarios included a full-load (FL) and an unladen (NL) ship, with draughts of 1.8 m and 0.65 m, respectively, passing at distances of 20, 40, and 60 meters from the monitoring point at two speeds: 5 km/h and 10 km/h. The ship used in the field survey is a commonly used freighter in Lake Taihu, characterized by a length of 32 meters, a width of 6.1 meters, and a height of 2.3 meters, with a full-load tonnage of 300 tons. To minimize wind disturbances during the shipping experiments, we selected a period with the minimal wind (vwind = 1.0 m/s).

本研究采用Nortek ADV测量了监测点上下层三维电流速度（u1、u2及w），采样频率为100赫兹。ADV设备置于湖床上方5厘米处，并固定于底部支架上，朝向下方。基于统计分析，将水平流速重新分配至主流u1（x方向）和横流u2（y方向）。垂直速度w代表z方向的流速，向上运动被视为正值。实地调查旨在辨识风力和船舶引起的扰动之间的差异。受风影响的测量数据收集于2018年7月26日，风速范围在0至11米/秒之间。2018年7月27日，我们进行了12次不同的船舶实验。船舶场景包括满载（FL）和空载（NL）船舶，分别具有1.8米和0.65米的吃水深度，从距离监测点20、40和60米的位置以5公里/小时和10公里/小时的速度通过。用于实地调查的船舶是太湖常见的货船，其长度为32米，宽度为6.1米，高度为2.3米，满载吨位为300吨。为最大限度地减少船舶实验中的风力干扰，我们选取了风速最小（vwind = 1.0米/秒）的时段。