Recent concept studies have demonstrated the potential to utilize a pre-swirl propulsor configuration with adjustable upstream stators to generate propulsor side forces. These studies led to a set of experiments and corresponding computations to validate this concept. Ducted and open pre-swirl propulsors were configured with an upstream stator row and downstream rotor. During normal operation, the upstream stator blades are all situated at the same pitch angle and pre-swirl the flow into the propulsor when generating a roll moment to counter the moment produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to both generate a mean stator side force and subsequently vary the axial velocity and swirl that is ingested into the inflow. The rotor then generates side forces in response to the inflow. Wind tunnel experiments were conducted to measure the steady, spatially varying stator wake flows for various stator geometric configurations using stereo particle image velocimetry. Computations utilized both potential flow and fully viscous 3-D (Reynolds Averaged Navier-Stokes, RANS) computations to predict the stator forces, velocity field and rotor response. Rotor design space investigations varied blade parameters including blade number, rake, skew and a combination of the two. RANS was used to then validate the final propulsor design with experimental data used to validate the computations. Computational data demonstrated that total side force coefficients on the order of 0.2 could be generated by the propulsor alone with results consistent with recent water tunnel measurements. This amount of control authority exceeds current control surface capabilities at 3 knots for Navy 21" unmanned undersea vehicles.
IEEE Journal of Oceanic Engineering, Volume 37, Issue 1, p. 122-138, January 2012.