Numerical simulation of bionic fish group movement in a land-based aquaculture tank

The previous researches on hydrodynamics in aquaculture tanks are mainly on the basis of empty tanks, but the movement of fish group has a significant impact on the hydrodynamics in the tank. In this study, a numerical model coupling the fish group and flow field in the tank was established based on computational fluid dynamics (CFD), simulating the fluctuation motion of fish group in the circular tank and square arc angle tank. The accuracy of this numerical simulation method was verified through a physical model experimental system. The hydrodynamics in two fish-free tanks (control group) and 14 cases under the influence of fish groups with different tail beat frequencies (TBF) were obtained and analyzed. The results indicate that the average velocity in the circular tank is always higher than that in the square arc angle tank, while the flow field uniformity coefficient (UC₅₀) of the circular tank is lower than that in the square arc angle tank except for cases of fish-free tank and tank with TBF = 3 Hz. Additionally, the circulation characteristics in the circular tank are always regular, but that in the square arc angle tank is not regular until TBF ≥ 2.5 Hz. Compared with fish-free circular tank, the presence of a school of fish in the tank significantly reduces the average velocity and UC₅₀ which are improved with the increase of TBF. In the square arc angle tank, the average velocity first decreases slowly and then increases rapidly, and UC₅₀ slowly increases and finally converges to 0.7. This study provides a numerical approach to simulate the movement of fish groups in the aquaculture tank, which can potentially promote fish kinematics research in the tank.