Propeller performance at low advance ratio

At low advance ratios that are much smaller than the advance ratio where the maximum efficiency of the propeller is obtained, large portions of the blades' cross sections operate at stall conditions. Using two-dimensional nonrotating airfoil data to calculate the propeller's aerodynamic performance at low advance ratios results in large differences between the calculated and measured performance. It turns out that because of rotation the stall characteristics of the airfoil are changed because Coriolis effects delay the boundary-layer separation. Based on previous investigations associated with wind turbines that have been reported in the literature, a simple correction model is presented. It is a straightforward matter to implement this model in existing strip models. The agreement between the calculated and measured results, at low advance ratios, is significantly improved after the introduction of the new model.