进径比对矩形圆弧角养殖池水动力特性影响

A numerical study of the effect of relative inflow distance on hydrodynamic characteristics in the single-drain rectangular aquaculture tank with arc angles

摘要:

为研究单管入流模式下，进径比(参数C/B，C为射流孔位置到养殖池壁的水平距离，B为养殖池短边边长)对单通道矩形圆弧角养殖池系统水动力特性的影响，实验运用计算流体动力学仿真技术构建单通道矩形圆弧角养殖池三维数值计算模型，应用平均流速、阻力系数和速度分布均匀系数等流体动力学特征量分析养殖池内(尤其是池底)的流场形态，并修正能量有效利用系数以评估养殖池系统的能量有效利用率。结果显示，将进径比参数C/B从0.00增大到0.05可有效改善养殖池内流场特性，进径比参数C/B设置在0.02~0.04之间有利于单通道矩形圆弧角养殖池系统获得最佳的流场条件。研究表明，进径比参数的较小优化可显著提高养殖池内平均流速与能量有效利用率，利于形成均匀稳定的流场。

关键词:矩形圆弧角养殖池;进径比;水动力特性;能量有效利用系数;计算流体力学

Abstract:

In order to explore the influence of the position of the water inlet device on the hydrodynamic characteristics of the single-drain rectangular arc angle aquaculture tank, a new parameter, the relative inflow distance C/B (C is the horizon distance from inlet to sidewall, B is the width of the rectangular tank) was proposed in this paper, and the complex flow field of near the sewage outlet were analyzed by fluid dynamics characteristics variables, and to measure the effective utilization rate of water in aquaculture tank, the effective utilization coefficient of energy ηe is put forward. Meanwhile based on the Reynolds averaged Navier Stokes (RANS) equation and RNG k-ε turbulence model, a three-dimensional numerical model of rectangular arc angle aquaculture tank was constructed. Computational fluid dynamics simulation technology was used to calculate and analyze the flow field environment in the constructed aquaculture tank. By adjusting the layout position of the inlet system, the flow field in the tank (especially at the bottom) was optimized, and the influence of the optimization of hydrodynamic conditions on the collection and discharge performance of the aquaculture tank system was analyzed. This base case is validated against the experimental velocity measurements using Acoustic Doppler Velocimetry (ADV) at predefined locations across the central vertical plane of the tank. On this basis, the hydrodynamic conditions of the aquaculture tank system were systematically analyzed by hydrodynamic characteristics, such as the average velocity, energy efficiency, velocity distribution uniformity at the bottom of the tank and so on. The numerical simulation results show that the average velocity and energy efficiency can be significantly improved by optimizing the relative inflow distance, which is conducive to the formation of uniform and stable flow field. And increasing the relative inflow distance parameter C/B from 0.00 to 0.05 can effectively improve the flow field characteristics in the aquaculture tank, and setting the relative inflow distance parameter C/B between 0.02 and 0.04 is beneficial to obtain the best flow field conditions for the single channel rectangular arc angle aquaculture tank system.The results show that the ratio parameter C/B in the range of 0.02~0.04 could effectively improve flow field characteristics of the system so as to get better hydrodynamic conditions for circulating aquaculture, and relatively minor construction changes could improve the hydrodynamic conditions of the aquaculture system and open up new ideas for obtaining the hydrodynamic environment conducive to fish welfare and production operation.

Key words:rectangular aquaculture tank with arc angle;the relative inflow distance;hydrodynamic characteristics;effective utilization coefficient;computational fluid dynamics(CFD)