Aerodynamics of flapping wings in forward flight

• Applicant: Dr.-Ing. Jong-Seob Han
• Subject Area: Fluid Mechanics
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 456038422

Flying insects are capable of both long-term hovering and high-degree of maneuvering with flapping wings. There have been a lot of studies on the flapping wings and their flight mechanics, bringing on a great improvement in the development of biomimetic drones. Nonetheless, it is still hard to say that the techniques accomplished so far are sufficient to describe the flapping-wing systems overall. Accordingly, the biomimetic drone development also has not jumped over a certain level. One notable issue in the recent trends in flapping-wing aerodynamics is that most studies still strongly confine own scopes to the hovering flight, despite the fact that staying particular point in space is very rare for most flying insects (they usually fly with a certain preferred – energy optimum – flight speed). The studies on the LEV also have heavily relied on the hovering state where a body stays at a fixed point and the wings move along the horizontal stroke plane without freestream. The advance ratio, which is also one primary element governing the LEV behavior, has been regarded as zero in these studies. Two distinctive kinematic features of flying insects in forward flight, i.e., the inclined and shifted-back stroke plane, which can significantly change the spanwise flow thereby impacting the LEV, have not yet been sufficiently investigated either. Few studies trying to reveal the effect of advance ratio had barely managed to report superficial things, because they relied on simplified motion profiles and marginally extended conditions from that in hover. A lack of such knowledge about forward flight brings on long-term stagnancy in aerodynamic model development. All the studies on flight dynamics are only able to cover near-hover maneuvers.With this program, this applicant proposes a thorough investigation on the aerodynamics of flapping wings in forward flight. The LEV characteristics on low-aspect-ratio flat plates at various kinematic and fluidic configurations in a fixed freestream will be explored in detail, and a novel aerodynamic model, which can encompass the LEV characteristics with respect to the advance ratio, aspect ratio, sweptback angle, and the angle of inclination of the stroke plane thereby being expandable to various flight modes, will be established. The flight stability analysis by using the aerodynamic model and morphological data of an example insect will also follow. This will give us better insights on the stability and controllability in forward flight.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Christian Breitsamter