Three-cylinder rotating system flows and their effects on a downstream dimpled airfoil

Abstract

Effects from turbulence levels created by a three-cylinder rotating system on the flow over a dimpled surface of an airfoil are reported. The three-cylinder rotating system effect is tested on the flow over a NACA0015 with leading-edge dimples at various angles of attack at Reynolds numbers of 0.5 × 105 and 1.0 × 105 in a low-speed wind tunnel. To the effect of mimicking free-stream flow perturbations, the three-cylinder system had small dimensional characteristics compared to those of the airfoil. Two-dimensional (2D) Particle Image Velocimetry (PIV) was used to characterize the flow with illumination from a dual-head Nd:YAG laser and imaging from two high-resolution PIV cameras setup to capture details of the three-cylinder system and the airfoil flow simultaneously. Results show wake characteristics that create complex unsteady and turbulent flows of various intensities as they rotate at various speeds in the free-stream. These free-stream flow disturbances establish the unsteady and turbulent flows that interact with the airfoil flow. The study finds substantial effects occurring for certain cylinder-system settings, airfoil angle-of-attack, and Re number, notably detecting a diminishing separation region and a decrease in its turbulence levels when compared to those for the flow without turbulence generated in the free stream.