Numerical and experimental study on the resistance characteristics of different autonomous underwater vehicles in towing tank conditions

When resistance tests of autonomous underwater vehicles (AUVs) are conducted in towing tanks, external support structures inevitably introduce hydrodynamic interference. This study investigates the influence of a sword-support structure on the resistance characteristics of an axisymmetrical rotary body underwater vehicle (ARBUV) and a blended-wing-body underwater vehicle (BWBUV) through both numerical simulations and towing tank experiments. Numerical simulations were performed to evaluate the resistance coefficients under different submergence depths and configurations of the sword-support structure. This study uniquely provides a quantitative and comparative analysis of structural interference across different AUV configurations, an aspect seldom addressed in previous research. Experimental measurements were conducted to validate the simulation results, showing strong agreement with deviations within 5%. The simulations provided detailed insights into the resistance coefficients, velocity field distributions, and surface pressure coefficients. The results show that the sword-support structure increases total resistance by more than 5% for both models, with BWBUV showing greater sensitivity. The sword-support alters local flow fields and pressure gradients, impacting both frictional and pressure resistance. Moreover, the interference mechanisms differ by configuration: pressure resistance in ARBUV is dominated by the sword-support, whereas in BWBUV, both the sword-support and the model connecting rod contribute comparably. These findings provide a reference for correcting structural interference in towing tank resistance tests of AUVs.