养殖鱼对养殖池内水动力影响的数值模拟

Numerical simulation of the effect of cultured fish on the hydrodynamics in a aquaculture tank

为研究养殖鱼对养殖池流场特性的影响,基于计算流体动力学(CFD)技术建立方形圆弧角单管养殖池及养殖鱼模型,采用多重参考系法(multiple reference frame,MRF)模拟鱼类在固定轨迹下的运动,并分析养殖池内养殖鱼的放养密度、个体体积和空间分布变化对养殖池流场特性的影响。结果表明:在养殖鱼个体体积和空间分布条件一定时,放养密度越大,养殖池内水体平均流速下降越大;在养殖池内养殖鱼放养密度一定时,鱼数量越多(个体体积小)时,鱼类的逆流游动产生的阻流作用越大,养殖池内平均流速下降就越明显;在养殖鱼放养密度、个体体积大小一定的条件下,养殖鱼在养殖池水体中层分布时,养殖池内水体的整体平均流速下降幅度和湍流强度增加幅度最大,养殖鱼在养殖池下层时,对平均流速和湍流强度的影响最小。研究表明,在循环水养殖过程中,应根据养殖池中养殖鱼的放养密度、个体体积和空间分布条件的变化,适时调整养殖池的进水速度,以维持养殖池内适于养殖鱼生存和生长的流场条件。

In order to investigate influence of fish on flow field characteristics of the aquaculture tank,the model of rounded square aquaculture tank with single inlet and cultured fish was established based on computational fluid dynamics(CFD),and the multiple reference frame method(MRF)was adopted to simulate the movement of fish under a fixed track.Influence of culture density,individual volume size and spatial distribution of fish in tanks on fluid flow characteristics in the aquaculture tanks was analyzed.Results revealed that the increase in culture density causes a great drop in average flow velocity in the aquaculture tanks under the same individual volume size and spatial distribution conditions.The upstream movement of fish makes high resistance to the flow and much greater drop in average flow velocity at the fixed culture density,and large school of fish(while the individual volume size is small).The maximal average flow velocity drops and turbulence intensity rise in the aquaculture tank caused by the school are observed at the fixed culture density and individual volume size,and distribution of the school of fish in the middle layer of the water.There were the least influences of the school on average flow velocity and turbulence intensity at the fixed culture density and individual volume size,and distribution of the school of fish in the lower layer of the water.Therefore,inlet current velocity of the aquaculture tank was properly adjusted,with culture density,individual volume size and spatial distribution to maintain flow field condition suitable for fish survival and growth.