3种网箱用网片的阻力性能与运动变化比较

Resistance characteristics and motion change of three kinds of nets used for sea cage

采用模型试验,3种不同网片分别为六角形目经编网片RHN、菱形目无结经编网片KRNDM、菱形目有结绞捻网片KTNDM,规格均为1.7mm(水平缩结长度)×1.7mm(垂直缩结高度)。在不同流速下,通过改变网片的水平缩结系数(Et,分别为0.65、0.707、0.60),对网片的阻力性能和运动变化(水平位移和垂直位移)进行研究。结果如下:(1)网片固定时,菱形目网片的阻力在水平缩结范围(Et=0.60～0.707)内,随着缩结增大而逐渐减小。六角形目网片阻力在3者中最大,有结绞捻网片阻力最小,六角形目网片阻力与缩结关系不明显。3种网片之间的阻力差值随流速的增加而增大。(2)缩结系数对于水平位移和垂直位移的影响随网片的结构差异而不同。缩结系数相同时,六角形目网片的水平和垂直位移均为最大,有结绞捻网片均最小。(3)网片的阻力与水平垂直位移受迎流面积的影响。在缩结系数范围内(Et=0.60～0.707)设计网片时首先应考虑网片结构和网线粗度,其次考虑结节,最后考虑缩结系数。

The Raschel Hexagonal Net （RHN）, the Knotless Raschel Netting in Diamond Mesh （KRNDM）and the Knotted Twisting Netting in Diamond Mesh （KTNDM）, with each of horizontal length of hanging and vertical length of hanging being 1.7 m, were studied by the model test in the flume tank. Based on the comparison through change of hanging ratios under different velocity of flow （Et as 0.65,0.707,0.60 respectively）, the results of netting resistance characteristics and motion change （horizontal displacement and vertical displacement）were obtained： （1）The resistance of Netting in Diamond Mesh was inversely proportional to the hanging ratio between the range 0.60 and 0.707 during fixation. The netting resistance of RHN was the highest of the three under the test conditions. The RHN was not well correlated with the hanging ratio. The difference value between every two nets increased with the velocity of flow. （2） The variation of Horizontal Displacement （HD） and Vertical Displacement （VD） influenced by hanging ratios differs with kinds of net. The HD and VD was inversely proportional to the hanging ratio between the range 0.60 and 0.707 during fixation. Under the same hanging ratios, the HD and VD of RHN was the highest, the next was for KRNDM, and the lowest was for KTNDM. The netting resistance, HD and VD were correlated with the line area. Within the range of 0.60 to 0.707 during the net designing process, the net structure and line thickness should be paid the most attention, the next is for net node, and the last is for hanging ratio.