Numerical Investigation of Propeller - Frame Arm Interaction in Hovering Flight

This study explores the interaction between a propeller and various frame arm geometries, which are typically used in multi-rotor applications. The influence of the arm on the propulsive performance of the propeller is investigated by using commercial computational fluid dynamics (CFD) solver ANSYS Fluent 17 in hovering flight. CFD results are validated for hover and vertical climb conditions with thrust and torque measurements conducted on a 16x4 carbon fiber propeller. Four different arm geometries (i.e., an Eppler arm, a cylindrical tube, a square tube, and a slotted square tube) are studied to investigate their effect on the propulsive performance of the propeller and the complete propeller-arm configuration. Regardless of the geometry, the arm enhances the thrust generation of the propeller for all propeller-arm distances considered in this study.  However, the total thrust of the propeller-arm configuration is smaller than the single propeller case due to drag exerting on the arm. In this respect, the Eppler arm configuration has the best performance in terms of the total force generation due to relatively low drag of the Eppler profile. The square arm configuration yields the highest thrust generation and propulsive efficiency for the propeller despite having the lowest total force generation.