Abstract: In the investigation，the CFD approach and the multi sliding mesh technique are used to numerically simulate the thrust characteristics of a ducted propeller in an underwater vehicle with a yawing motion，in which the ducted propeller is utilized as the major control mechanism to manipulate the vehicle and the propeller running motion is influenced by the fluid field of the components of the vehicle． Then，the effect of the underwater vehicle assembly on the thrust of the ducted propeller is discussed，and the law of issuing thrust of the ducted propeller in the vehicle with a yawing motion is examined． Moreover，the hydrodynamic interaction between the ducted propeller and the vehicle assembly is analyzed． Simulation results indicate that (1) the fluid field of the underwater vehicle assembly has a non-ignorable effect on the thrust characteristics of the ducted propeller，of which the torpedoshaped buoyant hull on the front of the ducted propeller is the major factor affecting its thrust characteristics; (2)within the hydrodynamic interaction region，the smaller the axial distance between the buoyant hull and the ducted propeller，the greater the thrust issued by the ducted propeller will be; and (3) the effect of the torpedo-shaped buoyant hull on the thrust characteristics of the ducted propeller is mainly exhibited by altering the rate of advance on the ducted propeller disk． When the thrust characteristics of the ducted propeller in the underwater vehicle system is discussed，only by taking the vehicle and the ducted propeller as an integrated assembly and by incorporating such an integrated assembly with the specific environment of the underwater vehicle system to conduct relevant computation，can the results in accordance with engineering application be achieved．

Key words: ducted propeller, underwater vehicle, CFD, hydrodynamics, yawing motion