Aero-Propulsive Interactions between UAV Wing and Distributed Propellers Due to Their Relative Position

Abstract

The purpose of this paper is the evaluation of the aero-propulsive effects on a UAV wing model with distributed propulsion. An array of three propellers is placed ahead of the leading edge of a rectangular wing with flap. The investigation was performed with high-fidelity numerical analyses to provide insights into the phenomenology and to screen the interesting positions to be validated in the wind tunnel. The propellers’ array is moved into twelve different positions, allowing longitudinal and vertical translations. The wing has an untwisted and constant section profile, with a single slot trailing-edge flap that is deflected into three positions. The flap span is entirely covered by the propellers’ blowing. Results show an increment of lift, drag, and pitching moment coefficients with distributed propellers enabled. For a given thrust level, the magnitude of such increments depends on the propellers’ positions, the flap configuration, and the angle of attack. The lift enhancement sought in distributed propulsion applications comes at the expense of a significant increase in drag and pitching moment magnitude. In some combinations, the wing’s contribution to the aircraft longitudinal stability is severely affected. Conversely, the propellers’ inflow is altered such that thrust is increased in all the investigated configurations, with a small reduction of propulsive efficiency.

Flow Structures and Aerodynamic Behavior of a Small-Scale Joined-Wing Aerial Vehicle under Subsonic Conditions

“…Based on the procedure outlined by [25], a minimum of three grids of increasing fineness, with a recommended grid refinement factor (l coarse /l f ine ) of approximately 1.3, are required to estimate the GCI. This methodology has been used for reporting the uncertainty of numerical simulation results for various aerodynamic phenomena such as vortex shedding of flapping wings [26], flow separation [27], and wing-propeller interaction [28].…”

An Experimental and Numerical Evaluation of the Aerodynamic Performance of a UAV Propeller Considering Pitch Motion

“…It is well known that the propeller placement with respect to the wing is a key design point for a propeller aircraft. In turn, the relative length from wing to the propeller might influence both the follower aerodynamic performance of the propeller and the torque budget for the aircraft [16,35]. Therefore, in this section, the relative length L from the wing's leading edge to the rotation center of the propeller was considered as a variable, and the values were 230 mm, 280 mm, 330 mm, and 380 mm, denoted as L 230 , L 280 , L 330 , and L 380 , respectively.…”