Wing load investigation of the plunge-diving locomotion of a gannet Morus inspired submersible aircraft

In this paper, we studied the wing root pivot joint's radial load of a submersible airplane which imitates the locomotion of gannet's Morus plunge-diving, by implementing a test device name Mimic-Gannet. The housing of the device was designed by mimicking the morphology of a living gannet, and the folding wings were realized by the mechanism of variable swept back wing. Then, the radial loads of the wing root were obtained under the conditions of different dropping heights, different sweptback angles and different water-entry inclination angles (i.e., the angle between the longitudinal body axis and the water surface), and the relationships between the peak radial load and the above three parameters were analyzed and discussed respectively. In the studied areas, the minimum peak radial load of the pivot joint is 50.93 N, while the maximum reaches up to 1135.00 N. The largest peak load would be generated for the situation of vertical water entry and zero wing sweptback angle. And it is of great significance to choose the three parameters properly to reduce the pivot joint's radial load, i.e., larger wing sweptback angle, smaller dropping height and water-entry inclination angle. It is also concluded that the peak radial load on the wing root is closely linear with the water-entry dropping height and the wing sweptback angle with a significant correlation. Eventually, the relationship between the wing load and the dropping height, water-entry inclination angle or wing sweptback angle, could be used to calculate the wing load about plunge-diving of a submersible aircraft, and the conclusions reveal the wing load characteristic of the gannet's plunge process for the biologists.