Control of the flow in the near wake of an airfoil at full stall using fixed trailing-edge plates


ÖZKAN G. M.

EXPERIMENTAL THERMAL AND FLUID SCIENCE, cilt.122, 2021 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

This work aims to control the unsteady flow structure of a NACA0012 under full stall by limiting the vortex roll up from its trailing edge. In this regard, plates with varying lengths at zero incidences were attached at the trailing edge of the airfoil at an angle of attack of alpha = 16 degrees and low Reynolds number of Re-c = 2.0 x 10(4). Under these conditions, the flow separates near the leading edge and rolls up (without reattachment) into the wake with a subsequent supercritical mode vortex shedding corresponding to the full stall condition. Planar PIV measurements were performed in a closed-loop water channel to analyze the effect of plate length on the wake characteristics of the airfoil. Turbulent flow structures of baseline airfoil and airfoil with various plate lengths (l/c = 0.1, 0.2, 0.3) were revealed and elaborated with time-averaged turbulent statistics, two-point correlations, spectral analysis, and instantaneous vorticity contours. According to the results, vortex roll-up from the trailing edge and corresponding turbulent structures were partially suppressed by the use of plates with l/c = 0.2 and l/c = 0.3 by elongating the vortex formation length. Besides, two-point correlations of fluctuating velocity components revealed that the use of trailing edge plates of l/c > 0.1 is effective in decreasing the size and magnitude of turbulent structures. Consequently, the turbulent fluctuations were found to be reduced, and the vortex shedding frequency was attenuated in the near wake of the airfoil.