Towards a controlled roughness for improved aerodynamic and acoustic performance of propellers at low Reynolds number

The influence of roughness on the aerodynamic and acoustic performances of propellers at low Reynolds numbers is studied, both with models and experimentally. Three propellers with different manufacturing methods are studied (wood, PLA, VeroWhite), and slight experimental differences are shown, like an increase of broadband noise for the wooden propeller (lowest roughness levels) and a decrease of lift for the PLA propeller (highest roughness levels). The numerical models are validated against experimental measurements, and these models are used to obtain the evolution of the boundary layer parameters along the chord. A laminar separation bubble is spotted on the suction side. Ideas for the design of an improved propeller with controlled roughness are discussed.