Thrust Response of a Vectored-Thruster Unmanned Underwater Vehicle

Towing tank/water flume experiments are conducted to characterize the dynamics
of a Remotely-Piloted Unmanned Underwater Vehicle (RPUUV) propelled by a
vectored-thruster system. Force and torque measurements are used to determine the
coefficients of drag, lift, yaw-moment and thrust of the vehicle as a function of the
vehicle yaw angle and the vectored-thruster rudder angle. Simultaneously, particle Image
Velocimetry (PIV) measurements of the propeller inlet flow are also performed to
examine the variation of flow conditions at the propeller inlet with rudder angle. The tests
are conducted at 0.150 rnls, 0.300 rnls, 0.515 rnls and 0.773 rnls. While the measured
drag coefficient is slightly higher than predicted by theory at low Reynolds number (1.44
x10^5 and 2.88 x10^5), 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 axis.