Numerical simulation of the hydrodynamics within octagonal tanks in recirculating aquaculture systems

• Published in: Chinese journal of oceanology and limnology Vol. 35; no. 4; pp. 912 - 920
• Main Author: 柳瑶 刘宝良 雷霁霖 关长涛 黄滨
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.07.2017; Springer Nature B.V
• Subjects: Above ground tanks; Abrasion; Accumulation; aquacultural engineering; Aquaculture; Aquaculture and Fisheries; Aquaculture engineering; Aquaculture systems; Aquaculture techniques; Area; Average velocity; Cleaning; Cleaning systems; Computational fluid dynamics; Computer applications; Corners; Design analysis; Dynamical systems; Dynamics; Earth and Environmental Science; Earth Sciences; energy; Energy losses; equations; Finite volume method; Flow pattern; Fluid dynamics; Fluid flow; Fluid mechanics; Hydrodynamics; Inlets (waterways); K-epsilon turbulence model; k-ε湍流模型; Mathematical analysis; Mathematical models; mixing; Numerical analysis; Oceanography; Optimization; Particle trajectories; Recirculating aquaculture systems; Sedimentation; Simulation; Tanks; Three dimensional models; Turbulence; Turbulent flow; Velocity; Velocity distribution; Water mixing; 三维数值模型; 八角; 平均相对误差; 循环水养殖系统; 数值模拟; 流体动力学; 计算流体力学; octagonal tanks; recirculating aquaculture systems; hydrodynamic simulation; rate of particle removal
• ISSN: 0254-4059; 2096-5508; 1993-5005; 2523-3521
• DOI: 10.1007/s00343-017-6051-3

A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system. The realizable k-e turbulence model was applied to describe the flow, the discrete phase model （DPM） was applied to generate particle trajectories, and the governing equations are solved using the finite volume method. To validate this model, the numerical results were compared with data obtained from a full-scale physical model. The results show that： （1） the realizable k-e model applied for turbulence modeling describes well the flow pattern in octagonal tanks, giving an average relative error of velocities between simulated and measured values of 18% from contour maps of velocity magnitudes; （2） the DPM was applied to obtain particle trajectories and to simulate the rate of particle removal from the tank. The average relative error of the removal rates between simulated and measured values was 11%. The DPM can be used to assess the self-cleaning capability of an octagonal tank; （3） a comprehensive account of the hydrodynamics within an octagonal tank can be assessed from simulations. The velocity distribution was uniform with an average velocity of 15 cm/s; the velocity reached 0.8 m/s near the inlet pipe, which can result in energy losses and cause wall abrasion; the velocity in tank corners was more than 15 cm/s, which suggests good water mixing, and there was no particle sedimentation. The percentage of particle removal for octagonal tanks was 90% with the exception of a little accumulation of 〈5 mm particle in the area between the inlet pipe and the wall. This study demonstrated a consistent numerical model of the hydrodynamics within octagonal tanks that can be further used in their design and optimization as well as promote the wide use of computational fluid dynamics in aquaculture engineering.