Effect of flapping frequency, Reynolds number and angle of attack on the aerodynamic force coefficients of a translating wing

This study presents a computational investigation of a flapping wing executing to and from horizontal motion with a fixed angle of attack or pitch orientation. The computational results compare well with the experimental results of Lua et al. (Exp Fluids 51(1):177–195, 2011). An attempt has been made to understand the effect of flapping frequency (f), Reynolds number (Re) and angle of attack (α) on flow features like vortex structures and wing–wake interaction. The present study is conducted for five different flapping frequencies, namely, f = 0.021, 0.21, 0.315, 0.42 and 2.1 Hz, four different chord-based Reynolds numbers, namely Re = 2000, 5000, 10,000 and 50,000 and two different angles of attack, namely α= 45 ^∘ and α= 60 ^∘. Vorticity contours display variation of vortex structures with change in flapping frequency. The temporal history of resultant force coefficients show distinct characteristics like amplitude modulation, linear growth and decay, inflexional behavior, dual peak behavior, etc. Frequency spectrum of the lift coefficient reveals that the flapping frequency is most dominant and it is accompanied by several harmonics. At higher Reynolds number, the spectrum displays broadband character. The power content of the dominant frequency increases with increase in flapping frequency and decreases with increase in angle of attack. A short investigation on the effect of three-dimensionality of the flow is also presented in this study. Additionally, three-dimensional eddy resolving simulations were performed with IDDES.