Unsteady Aerodynamics of Pitching and Plunging Airfoils: Impact of Motion-Related Parameters

Understanding the unsteady aerodynamics of airfoils during pitching and plunging motions is critical for optimizing their performance in various applications, including aircraft, micro air vehicles (MAVs), and wind turbines. Previous studies have shown that the performance of airfoils is influenced by factors such as frequency, amplitude, and the location of the pitching pivot. However, the specific impacts of these parameters under unsteady conditions remain unclear. Here we show that increasing the plunging/pitching frequency results in higher thrust (negative drag) coefficients. Our results indicate that thinner airfoils generate higher thrust compared to thicker ones. This finding is based on two-dimensional simulations at [Formula: see text] and small pitching/plunging amplitudes. Additionally, pitching at [Formula: see text] (where [Formula: see text] is the chord length of the airfoil) yields higher thrust than pitching at [Formula: see text], and pitching at [Formula: see text] results in near-zero thrust, suggesting that the pivot (under these specific low-[Formula: see text], 2D, low-amplitude conditions) should be close to the airfoil’s leading edge. The presence of an upstream vortex induces a sudden and significant increase in the lift coefficient as it approaches the airfoil, followed by a substantial decrease as the vortex moves in the wake, which can severely impact stability. These findings provide new insights into the design and operation of airfoils, particularly in environments with unsteady conditions and turbulence, though it is noted that these quantitative results are specific to the two-dimensional domain and tested parameter ranges.