航道清礁对西江鱼类保护区紊流体的影响

Influence of waterway cleaning up reefs on turbulent fluid in the Xijiang fish natural reserve

河底裸露的礁石增加水体紊动,有助于鱼卵正常形成,大量存在礁石的河段往往是鱼类栖息和产卵的重要场所。礁石也存在碍航的可能,航道清礁一定程度上影响水体紊动强度,改变鱼类栖息环境。为此,在重要鱼类栖息河段进行航道清礁需充分论证。以紊动动能作为评价水体紊动强度指标,开展西江中游珍稀鱼类保护区河段三维紊流数值模拟,计算并统计航道清礁工程前后水体紊动动能及不同强度的紊流水体体积,分析其变化规律及原因。研究结果表明,断面中紊动动能强度与水深成正相关关系;清礁工程导致河段中弱紊动动能的紊流水体体积增加,强紊动动能的紊流体积减小;底层水体紊动动能的变化量高于表层;强紊动动能水体体积减少的变化率大于弱紊动动能水体体积增加的变化率。

The reefs at the bottom of the river increase the turbulence of the water,which is conducive to the formation of fish eggs.The river with a large number of reef sections is usually an important place for fish to perch and spawn.Nevertheless,the reefs also have the possibility of impeding navigation.Cleaning up the reefs in the waterway has a certain influence on the turbulence intensity of the water body and changes the habitat of fish.Therefore,it is necessary to fully demonstrate the practice of waterway clear up reefs in important fish habitat sections.Using the turbulence kinetic energy as an index to evaluate the turbulence intensity of water body,the three dimensional numerical simulation of turbulent flow is carried out in the middle reaches of the Xijiang River where are also known as the river section of the rare fish reserve.At the same time,the turbulence kinetic energy of water body and the volume of turbulent water in different intensity are calculated before and after removing the reefs,and the change law and reason are analyzed.The results show that:the turbulent kinetic energy intensity has a positive correlation with the depth of water;the reef cleaning up project causes that the volume of water containing low turbulent kinetic energy increase and the volume of water containing high turbulence kinetic energy decrease;the variation of turbulent kinetic energy in the bottom water body is higher than that in the surface;the change rate of the volume reduction of high turbulent kinetic energy water is greater than that of the increase of the volume of the weak turbulent kinetic energy water.