Roll Stall for Low-Aspect-Ratio Wings

The longitudinal aerodynamics of micro aerial vehicles, although not fully understood, have been the subject of several studies in recent years; however, little work has been done to investigate the lateral loading. In this experiment, flat-plate wings with rectangular planforms of aspect ratios AR=0.75, 1, 1.5, and 3 and tapered planforms of λ=0.75, 0.5, and 0.25 were placed in the wind tunnel at a Reynolds numbers of 7.5×104. Angle-of-attack sweeps were performed at sideslip angles of β=0, −5, −10, −15, 20 and −35  deg, and the side force, yaw moment, and roll moment were measured. Although the side force and yaw moment coefficients (CSF and Cn) were typically negligible, the roll moment coefficient Cl was found to increase linearly with angle of attack before stalling in a manner reminiscent of a lift curve. This “roll stall”, which has not previously been observed for micro-aerial-vehicle-type wings, is attributed to the upstream tip vortex creating an additional lift component due to its impact on th...