Investigation of the Viability of Centrifugal-Type Thrusters for Small UUV Propulsion

This effort seeks to evaluate the viability of applying the principles of centrifugal, radial flow turbomachinery to propulsion/control effectors for small unmanned underwater vehicles (UUVs). Such a device would be well-suited to augmenting an autonomous vehicle's control authority in adverse underwater environments which may include surface waves and currents. Two candidate thrusters have been designed from scratch, fabricated, tested, and simulated for several scenarios of interest. These thrusters are “podded” in the sense that they are capable of rotating and directing thrust within the plane of rotation which would be tangential to a cylindrical vehicle's body surface. Physical and simulated experiments thus far involve thrusters which are isolated, that is, apart from a vehicle, in an otherwise quiescent fluid for basic thrust and torque loading measurements. Reynolds-averaged Navier-Stokes (RANS)-based finite volume methods with a multiple reference frame (MRF) approach for rotating flows were used to accomplish the numerical simulations. The v
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_ f eddy viscosity model was used for turbulence closure. For the in-water physical tests, the thrusters were mounted to the end of a cantilever-type load cell for thrust force measurement. Lessons learned from test results with the first candidate thruster led to design changes and subsequent improvements reflected in the second prototype while adhering to vehicle geometry constraints. Preliminary results indicate promising performance metrics for integration with UUVs with satisfactory efficiency.