Abstract: A simplified geometric model of a bat wing was utilized to study its morphology and deformation, along with its aerodynamic characteristics, using computational fluid dynamics methods. The wing consists of two parts: an inner parallelogram wing and an outer wing that is triangular-combined. The wing deformation was categorized into four categories, including changes in wing surface area, outer wing bending, chordwise camber, and wing twisting. Two flight modes were established based on experimental data, accounting for the kinematic parameter of slow and fast flight. The results demonstrate that the aerodynamic forces acting on the bat wing model in both slow and fast flight modes are similar in spatial-temporal distribution, with both lift and thrust generated during the downstroke duration. The forces during the upstroke duration are comparatively smaller. Thrust is generated entirely by the outer wing, whereas lift is generated not only by the outer wing but also by the inner wing. Additionally, it was found that the slow flight mode adapts to low-speed flight primarily by adjusting the angle of attack and fine-tuning the flapping frequency for different flight speeds. On the other hand, fast flight relies on frequency adjustment and fine-tuning of the angle of attack to balance the aerodynamic forces at various speeds. The analysis of the aerodynamic forces acting on the deforming bat wing contributes to a more profound comprehension of the mysteries of bat flight.

Key words: flapping, bat-like wing, aerodynamic force