Deformation of Nets With Bending Stiffness Normal To Uniform Currents
Deformation of Nets With Bending Stiffness Normal To Uniform Currents
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DOI：
10.1115/1.4028224
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发表时间：
2013-06
影响因子：
1.6
通讯作者：
L. Gansel;Østen Jensen;P. Endresen;M. Føre
中科院分区：
文献类型：
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作者：
L. Gansel;Østen Jensen;P. Endresen;M. Føre
过去几十年来，挪威养鱼业的巨大增长得到了养鱼场新设计和新材料的支持，使更大的鱼笼能够放置在更暴露的海域。今天，挪威大部分的鱼笼都是由尼龙制成的。尼龙网重量轻，相对容易处理，并且是所提出的网材料的低成本端。然而，尼龙网也有一些不幸的特点，如低耐磨性和有限的拉伸强度。因此，提出了新的网材料，以更好地防止逃逸，保护鱼类免受捕食者的攻击，提高鱼笼的稳定性和减少生物污染。这些材料中的一些在至少一个方向上是刚性的，并且仍然缺乏关于具有弯曲刚度的网在水流和波浪中的行为的知识。本研究的目的是确定如何与弯曲刚度网变形在不同的电流和变形如何影响网上的阻力，并比较结果与预测的数值模型。三种类型的网（PET，铜和钢）被夹在顶部的实心钢条上，但其他方面不受限制。反射标记被安装在网上，并且光学跟踪系统被用于在测试期间确定标记的位置，从而允许确定网面板的变形。用多轴力/扭矩传感器系统测量网面板上的力。网经受0.1和0.9 m/s之间的几种流速。结果表明，网的弯曲刚度和密度影响网的变形，因为这两个参数影响网上的阻力和重力之间的平衡。净变形导致投影净面积减小。由于变形率随流速在不同的网类型之间变化很大，因此在不同的流速下，测量的阻力和标准化为投影净面积的阻力值之间的差异对于不同的网遵循不同的关系。数值模型FhSim能够很好地预测具有弯曲刚度的网的净变形，并且表明FhSim不仅可以解释弯曲刚度对净变形的影响，而且该模型还捕获了当前具有弯曲刚度的网的结构动态。Copyright © 2013 by ASME
The tremendous growth of the fish farming industry in Norway over the past decades was supported by new designs and materials for fish farms, enabling bigger fish cages to be positioned in more exposed sea areas. Today, the nets of most fish cages in Norway are made from nylon. Nylon nets are lightweight, relatively easy to handle and at the low cost end of proposed net materials. However, nylon nets also have some unfortunate characteristics like low abrasion resistance and limited tensile strength. Thus, new net materials are proposed to better prevent escapes, protect fish from predator attacks, improve the stability of fish cages and reduce bio-fouling. Some of these materials are stiff in at least one direction and there still is a lack of knowledge about the behavior of nets with bending stiffness in currents and waves. The aim of this study was to determine how nets with bending stiffness deform in different currents and how the deformation influences the drag on the nets and to compare the results with predictions from a numerical model. Three types of net (PET, copper and steel) were clamped to a solid steel bar on the top side, but were otherwise unrestricted. Reflective markers were mounted on the nets and an optical tracking system was used to determine the position of the markers during the tests, thus allowing the determination of the deformation of the net panels. The forces on the net panels were measured with a multi-axis force/torque sensor system. The nets were subjected to several flow speeds between 0.1 and 0.9 m/s. It is shown that bending stiffness and density of nets affect net deformation, as both parameters impact the balance between drag and gravitational forces on the nets. Net deformation leads to a decrease of the projected net area. As the rate of deformation with current speed varies greatly between different net types, the discrepancy between measured drag and drag values normalized to the projected net area at different current speeds follows different relationships for different nets. A numerical model, FhSim was able to predict net deformation of nets with bending stiffness well and it is shown that FhSim could not only account for the effect of bending stiffness on net deformation, but also that the model captures the structural dynamics of nets with bending stiffness in a current.Copyright © 2013 by ASME