Numerical Study On Passive Flying Flow Field Of Dandelion

Some plants represented by dandelion use wind to spread their seeds,and their seeds can even float for thousands of meters in the wind.Dandelion seeds have a special pore-like bristle structure.When the air flows through,a separated vortex ring will be generated above.Dandelion stabilizes the air flow by its papus structure.In order to study the unique flight mechanism of dandelion seeds,this paper simplified the fluff structure of dandelion seeds into a rigid porous disk,numerically simulated the dandelion seed flight model by computational fluid dynamics(CFD)method.The results show that at a certain porosity,an axisymmetric and stable separated vortex ring will be generated above the dandelion seed model.According to the comparison between the data simulation results and the existing literature results,we found that the airflow velocity change trend above the model was similar,which verified the unique flying mode of dandelion seeds.On this basis,it continues to discuss the factors that affect the separated vortex ring,by changing the Reynolds number and porosity for numerical analysis,and comparing the aerodynamic characteristics.The results show that the formation of vortex ring has certain requirements on Reynolds number.When the porosity of the dandelion seed model below 79.93%,the vortex ring will separate.The maximum ratio of lift to gravity usually occurs in a specific range of Reynolds number and porosity.The discovery of this separated vortex ring marks the existence of a new flow behavior.