The Euler acceleration is noted to play a dominant role during the transient phase of the rotational maneuver of an insect wing. As such, this study aims to understand the influence of Euler acceleration on the transient loading and flow-field evolution over a rotating wing. By decoupling wing acceleration from steady-state velocity, the individual impacts of these parameters are systematically explored. The results reveal that Euler acceleration affects the transient dynamics differently depending on the steady-state velocity, suggesting the presence of distinct regimes. A new scaling parameter (${\alpha }^{*}$), defined as the ratio of Euler acceleration to convective acceleration, is introduced to delineate these regimes. The plot of the maximum lift coefficient ($C_{L_{\text{max}}}$) against ${\alpha }^{*}$ demonstrates the efficacy of this parameter, nearly collapsing the data into a single curve. This variation leads to the classification of two regimes: the quasisteady and acceleration-dominated regimes. In the quasisteady regime, secondary vorticity generation is crucial in dictating the transient dynamics, while no role of secondary vorticity is observed in the acceleration-dominated regime. The secondary vorticity is further dictated by the interplay between Euler and centripetal acceleration, with the former dictating the latter in the quasisteady regime, resulting in higher secondary vorticity development. This affects the growth rate of the leading-edge vortex (LEV), resulting in minimal variation of circulatory lift. In the acceleration-dominated regime, the absence of secondary vorticity growth leads to a continuous increase in LEV strength and hence the circulatory lift, which, combined with increasing noncirculatory component, results in an increase in $C_{L_{\text{max}}}$ with ${\alpha }^{*}$.

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• Aerodynamics
• Biological fluid dynamics
• Vortex dynamics