Assessing aerodynamic force estimation with experiments and simulations of flapping-airfoil flows on the verge of three-dimensionality

Abstract

This paper reports a combined experimental and numerical study of the flow over a rigid airfoil in flapping motion. The setup consists of a heaving and pitching airfoil at a moderate Reynolds number ([Formula: see text]), at a Strouhal number St = 0.1. The aim is to assess the accuracy of two-dimensional direct numerical simulations in predicting aerodynamic forces in a flow configuration, which is nominally two-dimensional but is at the verge of three-dimensionality. The assessment is carried out with experiments, including flow field and aerodynamic force measurements with particle image velocimetry and a load cell. The comparative study shows a good qualitative agreement between the experiments and the simulations at comparable Reynolds numbers both in terms of forces and flow fields, but with some quantitative differences. The quantitative discrepancies between experiments and simulation are analyzed and reduced to inherent differences between experimental and computational setups. It is observed that the significant differences are apparent almost exclusively in the wake evolution. Nonetheless, this is shown to have a minor effect on the aerodynamic force estimation. Overall, the trends observed when varying the mean pitch angle and the pitching amplitude are the same in both experiments and simulations. This suggests that two-dimensional/three-dimensional effects do not alter significantly the relationship between the unsteady flow mechanisms (i.e. leading edge vortex) and the aerodynamic forces in the parametric range considered here.

Three-dimensional effects on the aerodynamic performance of flapping wings in tandem configuration

“…The presence of the bodies is modelled by means of the immersed boundary method proposed by . The present algorithm has been successfully used for the simulation of aerodynamic flows, both in two- (Moriche et al , 2020 and three-dimensions Arranz et al 2018b,a;Moriche et al 2019). The computational domain is a rectangular prism, displayed in figure 3.…”

Three-Dimensional Effects on Plunging Airfoils at Low Reynolds Numbers

“…TUCAN has been successfully employed in flapping wing studies of infinite [14,24,25] and finite [26][27][28][29] aspect ratio wings.…”

Characterization of Aerodynamic Forces on Wings in Plunge Maneuvers

“…The wing is modeled using the immersed boundary method proposed by Uhlmann [24]. TUCAN has been extensively validated and employed for unsteady aerodynamics applications for infinite [25][26][27] and finite [28][29][30] aspect-ratio wings.…”