以CFD-DEM为基础的养殖槽排污性能及底坡优化

Pollution discharge performance and bottom slope optimization of aquaculture tanks for intensive pond aquaculture

由于能提高资源利用率,减少环境污染,低碳高效池塘循环流水养殖(IPA)作为一项新型养殖技术被大力推广。为了提高养殖过程中的集污排污效率,本研究拟采用构造负坡底面的方法对养殖槽结构进行优化。通过建立二维养殖槽简化模型,结合计算流体力学—离散单元法(CFD-DEM)模拟计算与核偏最小二乘(KPLS)建模方法,建立槽内垂向流速分布与底面坡度和粗糙度的关系模型。在此基础上结合泥沙运动理论,获得了槽内颗粒起动流速与单宽输沙率模型,在构建颗粒起动和输运两方面的性能指标后,利用基于偏好的多目标粒子群算法(DP-MOPSO)寻求最优底面坡度。寻优结果显示,随着底面粗糙度的增加,最优坡度略有减小,范围为0.013～0.015;仿真实验结果显示,构造最优底坡可有效提高颗粒的起动概率和槽体的颗粒运输能力,且对于表面较为粗糙槽体,坡型底面在颗粒起动方面的优越性更为显著,说明通过构建底坡来改变水流结构,从而实现养殖槽排污性能的优化是合理的。

Because of improving resource utilization and reducing environmental pollution,IPA(Intensive Pond Aquaculture)technology has been widely promoted as a new breed aquaculture technology.In order to improve the efficiency of pollution collection and discharge in the process of aquaculture,the method of constructing negative slope bottom is used to reconstruct aquaculture tanks.By establishing a two-dimensional simplified model of aquaculture tank and combining the CFD-DEM simulation and KPLS(Kernel Partial Least-Squares Regression)modeling method,a model that can reflect the relationship between the vertical velocity distribution and the bottom slope was established.On this basis,the model of the particle incipient velocity and the single wide suspended load transport rate in the tank was obtained by the theory of sediment motion.After setting up two performance indexes of particle motion and transportation,the DP-MOPSO(Preference-based Multi-objective Particle Swarm Optimization)method was used to get the optimal bottom slope.The optimization results show that with the increase of the bottom roughness,the optimal gradient is slightly reduced and the range is about 0.013-0.015.The simulation results show that the optimal bottom slope can effectively improve the moving probability and the transport capacity of particles,and for the rough surface,the superiority of the slope bottom is more significant.It shows that it is reasonable to optimize the discharge performance of aquaculture tanks by constr-ucting the bottom slope to change the flow structure.