Numerical study on the hydrodynamic characteristics of an unmanned underwater vehicle with twin side-by-side pump-jet propulsors

The development of unmanned underwater vehicles (UUVs), particularly those equipped with side-by-side twin-pump jet propulsion systems, is of great significance for enhancing comprehensive maritime capabilities. This paper employs a sliding mesh method to numerically investigate the hydrodynamic characteristics of a side-by-side twin-pump jet-propelled UUV, focusing specifically on flow field characteristics at two speeds: 4 and 6 kn. The study yields the flow field characteristics, unsteady thrust characteristics, and unsteady surface force characteristics of the side-by-side twin-pump jet-propelled UUV. The results indicate that there is no significant mutual interference between the twin propellers at the stern of this UUV, and the flow velocity and pressure conditions within the flow field are favorable. Under the influence of non-uniform inflow, the dominant frequency of the unsteady thrust pulsations generated by the propellers at the stern is the blade frequency, and the pulsation amplitude increases with increasing speed. Specifically, as the speed increases, both the time-domain and frequency-domain amplitudes of the thrust pulsations increase significantly; the thrust spectral amplitudes in the X and Z directions are approximately 50% of the axial (Y-direction) thrust frequency-domain amplitude. Regarding the transient surface force characteristics, the pressure pulsations on the propeller blades and fairing surfaces exhibit seven peaks and troughs within a single rotation cycle. This study provides effective numerical analysis methods and data references for the propeller design and hydrodynamic performance prediction and evaluation of UUVs with side-by-side propulsion systems.