Experimental Study Of Unsteady Aerodynamics For Flapping Flight And Exploration On Their Related Application

The surprising ability of insect flight is always a focus of biomechanics. Insect flight research can be divided into mechanism research and application research: the mechanism research can reveal the unsteady aerodynamics mechanism of flapping flight by theoretical analysis, insect observations, flapping model experiments and computational fluid dynamics; the purpose of the application research is to build flapping micro air vehicle (MAV) through the design and manufacture of artificial flapping mechanism which can simulate insect flight motion. Nowadays, the mechanism research and application research are both well developed: the unsteady high-lift mechanism in insect flight is proved, flapping MAV which has practical value is also developed. However, there still many problems about the insect flight have not been solved yet and need to be explored. In the present work, a series of experimental investigations were caried out for the insect observation, flapping model experiments and Flapping MAV development.A novel method called'Frame Difference'is proposed to solve the problem that the massive works of extraction from enormous amount of insect images can be treated in an acceptable period of time to obtain the morphological characteristics of insect flight. A noise-suppress operation between three adjacent frames and the internal characteristics of insects are fully used to realize the motion characteristics automatic extraction. The tests on some virtual and real insect image sequences indicated that: this method can well adapt the complex deformable contour of insect flight; and moreover, it still can provide good results even when the insect wings are partly transparency, or the body covers the wings or the high-speed camera has significant noise. The method can work without manual interference, and with no limitation for certain species of insects. Only relatively simple calculation is needed and in most cases it can give robust extraction results. The method is proved to be a feasible solution of massive insect images'morphological characteristics automatic extraction problem, and it can significantly reduce the time cost of the insect images sequence analysis.Considering the normal flapping models'problems that transmission complexity, huge size, lack of mobility and high cost, here a large-scale Hawkmoth flapping model driven by Servos is developed. Servos are very cheap, easy to control and they have compact structure. Using the intelligent software designed for the model control through personal computer, the Hawkmoth model can perform accurate flapping motion as real Hawkmoth. The model has similarity not only on the aerodynamics but also on the morphology. Furthermore, it can directly simulate the real Hawkmoth in the air, which is much closer to the real condition. The results of aerodynamics experiments for hovering Hawkmoth simulation with this model reveal that: the phase lag between stroke angle and angle of attack would have significant influence on the lift generation, and a suitable advance phase angle should be beneficial to obtain hovering lift; the motion curves are also important: real Hawkmoth motion mode can produce more lift than the simplified motion mode, so it is better for hovering flight; the wings'twist deformation along the wingspan wise during the hovering flight can't result to the remarkable increase of lift; the lift increase from excessive advance phase angle is very limited and it would increase aerodynamic power requirement. All the results show that: real Hawkmoth motion mode has the best aerodynamics performance among our experimental data, and This may explain the miraculous flight ability of Hawkmoth that derived from evolution.In view of the ultra small flapping mechanism research difficulty that hard to design and high cost of manufacture. Here a novel flapping mechanism named'electromagnetic drive wing'is proposed and justified. The mechanism integrates drive part and wing part into one film coil, and it is very easy to obtain flapping motion when the coil is controlled by current. In order to overcome the shortcoming of plane flapping mechanism that it can't control the stroke angle and angle of attack all together, a novel flapping mechanism called'Parallel Crank-Rocker'was successful developed. By the multi-parameters optimization and force measurement experiments, it was shown that the novel mechanism can perfectly simulate the insect flapping motion and can provide sufficient lift for the hovering flight requirement.In addition, some developments of flapping propulsion devices were challenged, in which flapping wing's high lift capability was referenced for the bionic underwater vehicle design to obtain high thrust. It was demonstrated that the great potential of flapping wing will be beneficial to the development of high performance bionic underwater vehicle.