Objectives This study aims to delve into the influence of various arrangement patterns and spatial configurations on the propulsion efficiency of bionic fish.

Methods This study employs the computational fluid dynamics (CFD) software Fluent with the finite volume method for discretizing governing equations and integrates advanced algorithms for high-precision numerical simulations. A user-defined function (UDF) was developed to simulate the flexible deformation of biomimetic fish boundaries. Additionally, innovative numerical simulations with various arrangement configurations were conducted to investigate their effects on flow field characteristics and propulsion performance.

Results In staggered arrangements of biomimetic fish, the thrust coefficient is low at Gx = 0 due to the cancellation of positive and negative vorticity between the two fish. In the range 0 ＜ Gx ＜ 1.0, the thrust coefficient of Fish #1 initially decreases and then increases, reaching a maximum at Gx = 1.0, while Fish #2 shows an initial increase followed by a decrease, peaking at Gx = 0.5. In triangular arrangements, Fish #1 experiences a decrease in thrust coefficient due to the low-pressure zone between the downstream fish, with smaller lateral spacing Gy leading to lower thrust. At Gx = 0, the thrust coefficient is low for the downstream fish, and it increases and then decreases with increasing Gx, indicating that strong interference only occurs at smaller Gx. In rectangular arrangements, the thrust coefficients of all four fish increase with larger Gy, suggesting that close lateral spacing results in adverse interference. At smaller Gx, the upstream fish benefit from the high-pressure zone created by the downstream fish, while the downstream fish are affected by the upstream fish's wake, causing the thrust coefficient to exhibit oscillatory behavior as Gx changes.

Conclusion The findings provide scientific guidance for optimizing inter-fish spacing to achieve hydrodynamic advantages and propulsion efficiency in clustered bionic fish for underwater operations. This study offers valuable insights for the research and development of efficient underwater cluster propulsion systems.