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The influence of the Reynolds number on both airfoils decreased as the turbulence intensity increased, whereas camber maintained a point of difference. Under increasing turbulence intensities, in contrast to prior flat plate research, the maximum lift coefficient was seen to decrease by up to 30% for the cambered airfoil, compared with a 5% rise for the symmetrical form. Testing was conducted at Reynolds numbers of 50,000–200,000, with turbulence intensities from 1.3 to 15%.
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Two airfoils, a NACA0012 and a NACA4412, were tested in relatively clean and highly turbulent flows in a wind tunnel. The present study was carried out to understand how this turbulent flow changes the performance of the UAV wing-in particular, how this influence may vary with the camber of the airfoil form. However, many UAVs fly at low altitude, where significant levels of turbulence are encountered due to terrain roughness.
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These aircraft fly below a Reynolds number of 250,000, where, in clean flow, the wing boundary layer undergoes laminar-to-turbulent transition for a significant portion of the wing chord. Small unmanned aerial vehicles (UAVs) are becoming more common as electronic systems decrease in size and weight.