The Lift Effects of Chordwise Wing Deformation and Body Angle on Low-Speed Flying Butterflies

This work investigates the effects of body angle and wing deformation on the lift of free-flying butterflies. The flight kinematics were recorded using three high-speed cameras, and particle-image velocimetry (PIV) was used to analyze the transient flow field around the butterfly. Parametric studies via numerical simulations were also conducted to examine the force generation of the wing by fixing different body angles and amplifying the chordwise deformation. The results show that appropriately amplifying chordwise deformation enhances wing performance due to an increase in the strength of the vortex and a more stabilized attached vortex. The wing undergoes a significant chordwise deformation, which can generate a larger lift coefficient than that with a higher body angle, resulting in a 14% increase compared to a lower chordwise deformation and body angle. This effect is due to the leading-edge vortex attached to the curved wing, which alters the force from horizontal to vertical. It, therefore, produces more efficient lift during flight. These findings reveal that the chordwise deformation of the wing and the body angle could increase the lift of the butterfly. This work was inspired by real butterfly flight, and the results could provide valuable knowledge about lift generation for designing microaerial vehicles.

Cardiopulmonary responses at various angles of cycle backrest inclination

The purpose of this study was to evaluate cardiopulmonary responses during submaximal cycle exercise at various angles of backrest inclination. Ten healthy Japanese men of mean age 25.9 yrs, height 170.6 cm, and body mass 66.1 kg, performed cycle exercises at a constant workload which reached the anaerobic threshold, at 20 degrees, 40 degrees, and 60 degrees of backrest inclination from the vertical plane, but the angle between the seat and back rest was kept at 110 degrees. The results were as follows: 1) Both cardiac output and stroke volume showed a higher value at the resting control state and during exercise as the backrest angle increased. 2) Oxygen consumption, carbon dioxide output, heart rate, gas exchange ratio, and oxygen pulse were not affected by the angle of backrest inclination. 3) Tidal volume at 20 degrees of backrest inclination was higher than at 60 degrees. 4) No significant differences were found in minute ventilation between each backrest angle. These findings suggest that changes in the backrest angle significantly alter cardiopulmonary parameters at rest and during exercise; in particular, an angle difference of 40 degrees may be enough to alter tidal volume, cardiac output and stroke volume, but not the minute ventilation.