Force/flow measurements on a low-speed, vectored-thruster propelled UUV

Force/torque and particle image velocimetry measurements are conducted on a vectored-thruster UUV model in a water flume to: 1) determine the hydrodynamic drag, lift and moment coefficients acting on the vehicle hull for zero rudder angle and yaw angles up to thirty degrees, and 2) measure the magnitude and direction of the thrust produced with the vehicle at a yaw angle of zero degrees and rudder deflection angles of up to thirty degrees. While the measured drag coefficient is higher than predicted by theory, the hydrodynamic coefficients data are expected to be useful in predicting the response of vehicles in the field. Additionally, the magnitude of the thrust vector varies nonlinearly with rudder angle and for nonzero rudder angles the thrust vector does not point in the same direction as the thruster. PIV images reveal that at rudder deflection angles of twenty five and thirty degrees the flow upstream of the propeller inlet has separated from the tail section and impinges at a large angle to the tail, thereby reducing both the thrust deflection angle as well as the total yaw moment acting on the vehicle