Aerodynamic Performance Analysis of a Main Propeller with Jointed Tip Mounted Blades Using Extended Blade Element Momentum Theory

Abstract

This study presents a comprehensive computational framework for evaluating the aerodynamic
performance of a primary propeller system integrated with tip-mounted secondary propellers, aimed at
mission adaptability without decreasing propulsion efficiency. The analytical model is grounded in the
Blade Element Momentum (BEM) method, augmented with Prandtl’s tip-loss correction to accurately
capture finite blade effects, and employs an iterative inflow solution scheme to ensure convergence of
induced velocity predictions. The formulation resolves aerodynamic forces at a fine spanwise resolution,
enabling detailed insight into the distribution of lift, drag, and local angles of attack along both the main
and secondary propeller blades. A distinctive feature of the configuration is the mechanical joint of the
secondary propellers to the primary blade rotation, resulting in each tip-mounted rotor experiencing a
complex effective freestream velocity composed of the aircraft’s translational speed and the tangential
velocity at the primary blade tips. The MATLAB-based implementation of the model provides thrust,
torque, and propulsive efficiency curves, as well as high-fidelity aerodynamic load maps for both the
main and secondary blades. Three-dimensional visualizations are generated to illustrate the spatial
loading patterns and aerodynamic interactions across the operational envelope. Results for a
representative baseline geometry demonstrate the influence of tip-mounted propellers on total thrust
augmentation, torque demand, and efficiency trends. The proposed methodology offers a rapid and
reliable tool for preliminary design optimization of unconventional multi-propeller architectures,
significantly reducing the reliance on computationally intensive CFD simulations while maintaining a
high degree of predictive accuracy.