Session: 01-08 Propellers and Open Rotors I

Paper Number: 151911

Effects of Leading-Edge, Suction-Surface Roughness on Propeller Performance for Unmanned Aircraft Applications 

This paper presents a study of roughness on the leading edge, upper suction-surface of a propeller intended for unmanned aircraft applications, evaluating the effect on thrust coefficient and propeller efficiency. The motivation for this study is to understand the potential impact of ice accretion on propeller performance relevant to unmanned aircraft flight conditions, occurring at low Reynolds numbers. Under such conditions, the propeller can be vulnerable to boundary layer separation at local spanwise locations. The propeller test article used throughout this study is a 16-in diameter propeller with a 10-in pitch. Initial analysis of expected baseline propeller performance was conducted using Blade Element Momentum Theory. Surface roughness was simulated with protruding domes, having height and spacing based on blade element chord length. The area covered by the field of domes varied by spanwise and chordwise extents to determine the correlation between propeller performance and amount of surface roughness. The spanwise extent begins at 30% of the propeller span. Experiments were conducted in a low-subsonic wind tunnel with a 3-ft by 3-ft test section and propeller dynamometer instrumented for torque, thrust and shaft speed. Initial experiments were conducted with a stock, unmodified propeller to compare baseline experimental and analytical results. Propeller test articles were fabricated using a resin 3D printer such that the structural stiffness and surface finish differed slightly from the stock propeller. A baseline, fabricated test article without roughness was tested for comparison with the stock propeller. Subsequent fabricated test articles with roughness were compared to the baseline fabricated test article to account for material and manufacturing influences. The experimental procedure varied airspeed from 20-ft/s to 50-ft/s and rotational speeds from 3000-RPM to 6000-RPM to span a Reynolds number range. Results show propeller thrust coefficient and efficiency relative to advance ratio. In some cases, surface roughness had a positive influence on propeller performance, presumably by passively energizing the boundary layer. A numerical study was performed to visualize the effect of surface roughness on the flow and provide further insight into key aerodynamic mechanisms.  Observations from this study provide insight into effects of surface roughness, such as ice, on propeller performance. Conclusions from this evaluation inform unmanned aircraft operators of potential effects on low flight speed performance in adverse weather, prompting propeller selection and design changes.

Presenting Author: Austin Rouser Oklahoma State University

Presenting Author Biography: Austin Rouser has graduated in 2024 with a BS in mechanical engineering and a BS in aerospace engineering at Oklahoma State University (OSU). As an undergraduate, he worked as an undergraduate research assistant, and he worked with the OSU Flight Center as a maintenance shop assistant. He is currently working as a process engineer with the U.S. Air Force at the Oklahoma City Air Logistics Center.

Authors:

Austin Rouser Oklahoma State University
Kurt Rouser Oklahoma State University
Nathan Wisniewski Oklahoma State University
Joshua Melvin Oklahoma State University
Ryan Paul Oklahoma State University