Hydrodynamic performance and experimental validation of a wire-driven bio-inspired underwater vehicle with fish-like propulsion

Wire-driven bio-inspired underwater vehicles offer low-noise propulsion and maneuverability, but their hydrodynamic behavior remains insufficiently understood. A three-dimensional computational fluid dynamics model was developed in STAR-CCM+ to evaluate straight-swimming and turning performance. Under imposed inflow conditions, oscillation frequency and body-bending amplitude were varied to assess cycle-averaged streamwise force. Asymmetric bias angles were introduced to evaluate side force, yaw moment, and streamwise-force retention. Increasing frequency and amplitude generally increased mean streamwise force, whereas low-frequency motions produced negative or near-zero values at the reference inflow. Straight swimming was associated with a reverse Kármán vortex street and downstream momentum jet; turning involved asymmetric wake deflection and vortex distortion. Still-water prototype experiments confirmed the predicted swimming-speed trends with frequency and amplitude. These findings inform kinematic design and maneuverability improvement for wire-driven underwater vehicles.