Low-Order Modeling of the Unsteady Aerodynamics in Flapping Wings

Reduced-order modeling of the unsteady aerodynamics generated by three-dimensional flapping wings undergoing three-dimensional motion is investigated. A low-order quasi-steady model based on rotational lift and a revised version incorporating dynamic stall are compared with experimental data generated with matching kinematics. The dynamic-stall-based model in general showed the ability to produce force curves with scale and shape similar to the experimental data, capturing most salient features but not properly resolving some of the peaks and troughs that appear post-half-cycle. The rotational lift-based model in general closely resembled the static force curves at the midcycle and overestimated the salient features around the half-cycle. This varying behavior between models is due to the primary differences in the influencing factors of the rotational lift and dynamic stall terms. These differences are exploited in a combined model that shows greater agreement with the experimental data.