タンポポ冠毛の隙間が飛行にもたらす効果

抄録

Dandelion is a classic example of a wind-dispersed plant and enabling long-distance seed dispersal. In 2018, Cummins et al. reported their results of freely flying tests and fixed tests on both real dandelion seeds and a separated vortex ring was found above the pappus of the dandelion using flow visualization techniques. The separated vortex ring is the main aerodynamic feature of the dandelion seed which enables its flight. However, the effect of the gap structure of the pappus on the vortex generation has not been fully understood. In the present study, in order to investigate the effect of the pappus’s porosity on flow structure in the wake of pappus, drop tests and flow visualization experiments were conducted using a vertical airflow pipe for the pappus with different porosity. The experimental samples are artificially changed porosity of pappus by partially removing filaments for the real (inhabit in nature) dandelion pappus. The pappus’s porosity affects the strength of vortices generated in the wake of the pappus and the vortex growth during posture changes in free-fall motion. This vortex behavior is strongly related to the aerodynamic forces acting on the pappus.