Development of an Empirical Propeller Thrust Model Using Experimental Measurements and Computational Fluid Dynamics

Abstract

Autonomous unmanned aerial vehicles (UAVs) are playing an ever-increasing role in naval operations. In order for these UAVs to safely operate autonomously in a wide range of conditions, robust control systems must be combined with a high-fidelity model of the thrust from the vehicle’s propellers. The vast majority of experimental and computational fluid dynamics (CFD) studies on propeller thrust documented in the open literature have studied propeller thrust only as a function of RPM and axial advance ratio. For a UAV operating in the vicinity of the moving deck of a ship, operating conditions will also include crosswinds across the propeller disks and effects from the vehicle proximity to the ship deck. Currently, no experimental or computational studies provide an all-encompassing study into the entirety of a propeller’s operating envelope. In this thesis, CFD is utilized to investigate the thrust performance of a small-scale propeller as a function of RPM, axial advance ratio, transverse advance ratio, and ground proximity. Experimental thrust measurements were also performed in order to validate thrust trends and provide an anchor for the thrust data from CFD. The thrust data from the CFD showed exceptional qualitative agreement with available experimental data while generally overpredicting thrust by 20 percent. The combination of the experimental and CFD data allowed for an accurate empirical thrust model to be developed that will permit UAVs to safely and effectively operate in a wide range of operating conditions. The results presented in this thesis highlight the critical role that both experimental and computational tools can play in propeller design and analysis.