潜水推流器作用下大型圆形养殖池的流场特性

Characteristics of flow field in a large-scale circular aquaculture tank under action of submersible thrusters

为了探究潜水推流器作用下大型圆形养殖池内的水动力特性,利用研发的无人船搭载声学多普勒流速剖面仪(acoustic doppler current profiler,ADCP)系统现场测定了潜水推流器数量(n=2、4)对圆形养殖池不同水层(h=1.5,2.0,2.5 m)流场分布特性的影响。结果表明:当推流器数量为2个时,大型圆形养殖池1.5、2.0、2.5 m水层池边流速分别为0.4、0.3、0.1 m/s,当推流器数量为4个时,1.5、2.0、2.5 m水层池边流速分别为0.6、0.4、0.3 m/s;水平方向上,养殖池流速随着池边缘距池中心距离的减小而逐渐减小,垂直方向上,流速随着水层深度的增加而逐渐降低;平均流速分布显示,无论利用2个还是4个推流器推流,都能在养殖池内产生旋转流,但高流速仅仅在养殖池边缘附近,且养殖池中心附近的流速接近于0,导致污物很难到达养殖池中心的排污口。研究表明,推流器数量与大型圆形养殖池不同水层流场分布特性密切相关,养殖池内不同水层的平均流速均随着推流器数量的增加而增大;圆形养殖池由中心到池壁均产生较为明显的流场分区现象,高流速区域分布在养殖池表层池壁附近;大尺寸圆形养殖池在初始水动力条件、推流器数量一定时,环流仅在池边产生,池塘中间位置产生环流较小。本研究结果可为大型圆形养殖池内潜水推流器布设方式的改进提供参考依据。

In order to investigate the hydrodynamic characteristics of a large-scale circular aquaculture tank under the action of submersible thrusters,the effects of number submersible thrusters(n=2,4)on the flow field distributions in different water layers(h=1.5,2.0,2.5 m)of a large-scale circular tank were determined in situ by using the acoustic doppler current profiler(ADCP)system developed for unmanned vessels.The results showed that the flow velocities at the edge of the tanks in the 1.5,2.0,and 2.5 m water layers were about 0.4,0.3,and 0.1 m/s,respectively,the flow velocities at the edge of the tanks in the 1.5,2.0,and 2.5 m water layers were about 0.6,0.4,and 0.3 m/s in the tank with 4 thruster,respectively,with gradual decrease in the flow velocities with the distance of the edge of the tanks from the tank centre in the horizontal direction,and the flow velocities in gradual decrease with the increase in the water layer depth in the vertical direction.The average flow velocity distributions characteristics of flow field distribution showed that rotational flows were generated in the aquaculture tanks regardless of two or four thrusters were disposed,but the high flow velocities were only found at the edge of the tanks,with gradual decrease in the flow velocity with the increase in water layer depth.The mean flow velocity distribution showed that no matter two or four thrusters to push the flow,rotating flow was generated in the aquaculture tank,with the high flow velocity only near the edge of the tank and close to 0 of the flow velocity near the centre of the tank,thus resulting in difficulty of the pollutants removal outfall in the centre of the tank.It was shown that the number of thrusters was closely involved in the flow field distribution characteristics of different water layers,with increase in the average flow velocity of different water layers in the aquaculture tank with the increase in the number of thrusters from n=2 to n=4.More obvious flow field zoning phenomenon from the centre to the wall of the tanks was observed in the circular aquaculture tanks,and the high flow velocity area was distributed near the wall of the aquaculture tanks surface layer.There were circulating currents only in the edge of the large circular aquaculture tanks and smaller circulating currents in the middle tanks under the initial hydrodynamic conditions and certain number of thrusters.The results of this study can provide a reference basis for the improvement of submersible thruster deployments in large-scale circular tanks.