The aerodynamic properties of a NACA 0012 airfoil, both stationary and unsteady, in ground effect (for nondimensional ground clearance h/c ≤ 60%) were investigated experimentally at Re = 98,000. For the stationary airfoil, the ground proximity led to a reduced (or enhanced) lift and an increased nose-up (or nose-down) pitching moment for α < 6° (or α > 6°). The drag was, however, always increased in ground effect. For the oscillating airfoil, a substantial change in the aerodynamic loadings, especially during downstroke, was observed for h/c ≤ 30%, leading to a greatly reduced Cl-hysteresis compared to the baseline airfoil. As the case of the stationary airfoil, the lift increase was mainly caused by the RAM pressure effect, but to a greater extent. The dynamic-stall vortex was also weakened and broke down earlier with reducing h/c, rendering an enlarged separated flow compared to the baseline airfoil. The results are of importance in understanding the ground effect on an unsteady airfoil.
Impact of ground proximity on the aerodynamic properties of an unsteady airfoil
2018-08-01
17 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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