Spanwise variations in profile drag for airfoils at low Reynolds numbers

Extensive wake surveys of the peculiar drag characteristics of low Reynolds number airfoil flows reveal the prominent role of the laminar separation bubble and airfoil geometry in spanwise drag variation. The amplitudes of the oscillations decrease with the increase in Reynolds number, and the spanwise locations of the oscillations shift with changes in the angle of attack. The largest fluctuations are observed for low angles of attack and at the lowest point of the low drag range. A weak agreement is observed in profile drag measurements between different wind-tunnel facilities.