Investigation of heaving amplitude effects on the lift characteristics of a hovering wing with an elliptical cross-section

The aerodynamic lift coefficient (C_L) characteristics of a hovering wing with an elliptical cross-section are assessed experimentally and numerically to investigate the effect of heaving amplitude (h₀) on the C_L. The wing has a rectangular planform with a chord length (c) of 0.04 m and an aspect ratio of 10. The wing plunges and pitches sinusoidally in a quiescent fluid. The pitching amplitude (θ₀) is fixed at 30° and the plunging amplitude (h₀/c) is varied between 0.375 and 0.750. The hovering frequency varies between 1.6 Hz and 0.8 Hz, corresponding to the Reynolds numbers (Re) of 3016 and 6032. The resulting C_L on the hovering wing exhibits distinct temporal variations across these cases. For h₀/c = 0.375, irrespective of Re, the C_L curve shows a single peak during the downstroke and dual peaks during the upstroke. For h₀/c = 0.750, irrespective of Re, the C_L curve shows a dual peak during the downstroke and a single peak during the upstroke. These results demonstrate that modest variations in heaving amplitude can significantly modify unsteady lift generation and vortex interaction dynamics. Details of the Lagrangian coherent structures and their correlation with C_L will be discussed during the presentation.