Quasi-Steady Approximation of Forces on Flat Plate due to Large-Amplitude Plunging Maneuvers

Abstract

Force histories were measured for a flat-plate wing during several different sine-squared plunge maneuvers that significantly exceeded the limits of small-perturbation and small-angle approximations. These lift curves were characterized using a two-term decomposition based on the quasi-steady components of the small-perturbation analytical model by von Kármán and Sears. Despite the unsteadiness of these maneuvers, the quasi-steady representation fit well to force histories from most of the tested cases. The amplitude of each term of this decomposition was compared to predictions made by potential flow theory and empirical models. Agreement between potential flow models and the unsteady measurements extended to plunge maneuvers with moderate unsteady to steady velocity ratios.