Effect of the waterjet propulsor ducts on the hydrodynamic performance of a wheeled amphibious vehicle

The integration of waterjet propulsor ducts modifies the underbody openings and near-bottom inflow of wheeled amphibious vehicles (WAVs), but its effect on the hydrodynamic performance and wake dynamics remains insufficiently understood. In this study, towing tests and validated numerical simulations were combined to examine three configurations: a bare vehicle without ducts (WAV#1), a single-duct vehicle (WAV#2), and a twin-ducts vehicle (WAV#3). The numerical model reproduced the measured resistance and representative free surface patterns, with a maximum resistance deviation of 2.17%. The results show that ducts increase the resistance coefficient, especially at high speed. At Fr = 1.307, the resistance coefficients of WAV#2 and WAV#3 are 5.5% and 8.9% higher than that of WAV#1, respectively. The sinkage first decreases and then increases with Fr, whereas the trim angle increases and then decreases, peaking near Fr = 1.121. At this condition, WAV#2 exhibits trim angles 10.7% and 17.8% higher than WAV#1 and WAV#3, respectively. Flow-field analyses indicate that the single-duct produces localized suction and inlet separation, while twin-ducts intensify transverse flow competition, pressure coupling, wake spreading, and internal velocity distortion. These findings clarify the hydrodynamic mechanism of waterjet propulsor duct arrangements and provide guidance for optimizing waterjet propulsion layouts in WAVs.