Study on the Effect of Motion Asymmetry on the Hydrodynamic Performance of Flexible Flapping Wing Propulsion

The pectoral fin flapping of manta rays and other organisms using the Median and Paired Fin locomotion (MPF) has the characteristics of space-time asymmetry. According to this property, this paper first defines the time and space asymmetry coefficients to describe the motion asymmetry, and then constructs a three-dimensional silicone flexible flapping model to conduct hydrodynamic experiments, and obtains the flapping thrust, lift and pitching torque under different space-time asymmetric conditions. Experimental results show that spatial asymmetry leads to a slight decrease in thrust, time asymmetry leads to a slight increase in thrust, both space and time asymmetry lead to a slight decrease in lift and thrust ratio. The increase of the asymmetric coefficient of time and space will gradually increase the pitching torque of the lower flapping, and the pitching torque of the upper flapping will decrease, indicating that the asymmetric movement of the flapping wing has no obvious effect on the thrust, and the effect on the pitching torque affecting the attitude is significant. The behavior of pitching attitude adjustment by asymmetric flapping by marine organisms with MPF as the propulsion mode was verified.