Objectives This study proposes a vortex-generator array design to effectively suppress the enhancement of circumferential non-uniformity and flow unsteadiness in the propeller wake fields, which are caused by the downstream evolution of horseshoe vortices generated at the tail fins of underwater vehicles. The proposed configuration aims to achieve hydrodynamic noise suppression and improve the stealth capability of the vehicle through precise flow control.
Methods First, the present work is performed on the SUBOFF standard submarine configuration and a pump-jet propeller. A high-fidelity flow field simulation was conducted using the finite volume method (FVM) and an improved delayed detached-eddy simulation (IDDES) turbulence model, establishing a high-precision numerical model for low-frequency excitation forces generated by underwater vehicle thrusters. The model was validated against published experimental data, showing an error within 4%. Second, the vibration reduction and acoustic suppression effects were evaluated by comparing the vortex-generator-equipped configuration with the basic configuration through excitation force and noise analyses, with the underlying mechanism explained in terms of flow field evolution. Subsequently, several VGA configurations with different numbers of vortex generators were simulated to optimize their quantity. Finally, high-speed simulations were performed to investigate the speed dependency of the VGA's vibration and noise reduction performance.
Results The results show that the vortex-generators significantly reduced vibration and noise. The optimal configuration achieved a 68.56% reduction in the rotor excitation force peak at the first blade-passing frequency (BPF), while the far-field radiated noise decreased by 1.81 dB in the transverse plane and 2.84 dB in the horizontal plane at an equivalent sound pressure level measured 1 m away.
Conclusions The vortex-generator array effectively improves the wake field by segmenting large-scale vortex structures, thereby mitigating thruster-induced vibration and noise. The number of vortex generators should be optimized, not simply maximized, and the performance remains stable at high speeds. This study provides a novel approach for reducing noise in underwater vehicle thrusters.
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