【作者】 刘扬；

【导师】 黄国兴；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2021， 硕士

【摘要】 在海洋牧场的建设过程中,人工鱼礁是主要的人工构造物,常采用开孔异形混凝土结构或框架式钢结构,投放于海底用以模拟自然礁石,为海洋生物提供良好栖息环境、保护并增殖鱼类产量,可以修复和改造原有的海洋生态环境。人工鱼礁投放后,将受到潮流、波浪等自然水动力因素的作用,并对原海域周围的流场产生影响。首先人工鱼礁会对水流起到阻碍作用,礁体前方将形成局部的上升流。上升流将海底的营养物质带到上层海域,促进了上下层水体间的营养物质交换,提高了礁区附近海域的营养物质浓度,有利于鱼群聚集觅食。其次水流在礁体后方将形成一定范围的缓流区。缓流区内的水流速度缓慢,有助于营养物质沉积,为鱼类提供栖息和繁殖的空间。人工鱼礁对周围水动力状态的改变性能被称之为“流场效应”。目前国内外对人工鱼礁的研究多集中于混凝土开孔结构形式的鱼礁,而现有人工鱼礁的流场效应远未达到理想程度,对天然水动力环境影响较大。研发具有优质流场效应且对投放海域水动力影响最小的新形式鱼礁,成为海洋牧场建设中重要的研究问题之一。本文针对六角型人工鱼礁这一新型鱼礁的流场效应开展研究。首先采用物理模型试验的方法,基于粒子图像测速技术(PIV),测量两种摆放方式及多种来流速度下六角型人工鱼礁的流场;其次,采用计算流体力学软件FLUENT建立相应的数值模型,通过拓展组别,探讨六角型人工鱼礁相对尺度、相对来流速度、导流板角度对流场效应的影响。并与现有典型人工鱼礁的流场效应进行比较。研究结果表明:与现有典型人工鱼礁比较,六角型人工鱼礁内部的流场流态简单,且鱼礁前后未有大尺度涡形成,适宜构造柔和的流场;其流场效应受来流流速和方向的影响较小,具有良好的方向适应性;迎流角在0°～30°变化时,最大上升流速在20%～40%来流速度范围内变化;缓流区范围大体在1.5倍礁高×3～5倍礁长范围;六角型人工鱼礁内流场效应较佳对应的几何参数为:外部孔径比在0.50～0.64的范围内变化时,最佳孔径比为0.58较佳;导流板角度在21.8°～33.2°的范围内变化时,角度设置为30.9°时较佳。更多还原

【Abstract】 Artificial reefs are one of the main artificial structures used in the construction of marine pastures,often using open-hole shaped concrete structures or framed steel structures,placed on the seabed to simulate natural reefs,providing a good habitat for marine life,protecting and increasing fish production,and restoring and transforming the original marine ecological environment.The artificial reefs will be subject to natural hydrodynamic factors such as currents and waves,and will have an impact on the flow field around the original area.Firstly,the artificial reef will act as a barrier to the current and a local upward flow will be formed in front of the reef.The upward flow will bring nutrients from the bottom to the upper waters,promoting the exchange of nutrients between the upper and lower waters and increasing the nutrient concentration in the waters around the reef area,which is conducive to fish gathering and feeding.Secondly,the current will form a certain range of slow flow area behind the reef.The Slack flow region in this zone helps to deposit nutrients and provides space for fish to live and breed.The performance of artificial reefs in changing the surrounding hydrodynamic state is called the "flow field effect".Most of the research on artificial reefs at home and abroad is focused on reefs in the form of concrete openings,while the flow field effect of existing artificial reefs is far from ideal and has a large impact on the natural hydrodynamic environment.The development of new forms of reefs with high quality flow field effect and minimal impact on the hydrodynamics of the released area has become one of the important research problems in the construction of marine pastures.This paper investigates the flow field effects of a new type of reef,the hexagonal artificial reef.Firstly,a physical model test is used to measure the flow field of the hexagonal artificial reef under two placement methods and various incoming velocities based on particle image velocimetry(PIV);secondly,a numerical model is established using the computational fluid dynamics software FLUENT to investigate the effects of the relative scale,relative incoming velocity and angle of the deflector on the flow field effect of the hexagonal artificial reef by expanding the group.And the flow field effects were compared with those of existing typical artificial reefs.The results of the study show that:Compared with existing typical artificial reefs,the flow pattern inside the hexagonal artificial reef is simple,and there is no large-scale eddy formation in front and behind the reef,which is suitable for constructing a soft flow field;its flow field effect is less affected by the incoming flow velocity and direction,and has good directional adaptability;the maximum upward flow velocity varies from 20% to 40% of the incoming flow velocity when the head-on angle varies from 0° to 30°;the range of the slow flow area is roughly The best geometric parameters for the effect of the flow field in the hexagonal artificial reef are: the external aperture ratio varies from 0.50 to 0.64,with the best aperture ratio being 0.58;the angle of the deflector varies from 21.8° to 33.2°,with the best angle being set at 30.9°.更多还原