Simulation Of Parachute Opening Process Based On Fluid-solid Coupling Method

Parafoil is widely used in aerospace,civil and military fields because of its high lift-drag ratio,precise landing performance and lightweight structure.The parachute process is one of the key procedures,and its performance research has become a necessary content.At present,the research of parachute opening process mostly depends on airdrop test,and the understanding of deployment mechanism is limited.In this paper,the fluid-solid coupling simulation of parachute opening process based on ALE method is first carried out.Firstly,the feasibility test of the ALE fluid-solid coupling method for the parafoil opening process is carried out.A parachute accordion folding model and the flow field model are established to simulate the parachute opening process with different incoming flow velocities.The influence of grid density on the numerical results is studied.The dynamic changes of the parachute shape,load and elongation during parachute opening are obtained.The numerical results are in good agreement with the literature test results,which proves the correctness and effectiveness of the ALE method in the application of the fluid-solid coupling of the parafoil.Secondly,the ALE finite element method is used to study the parachute opening process in wind field.The "compound boundary" is used to simulate wind field conditions.The parachute opening process in different wind directions is simulated by fluid-solid coupling numerical simulation and the dynamic changes of parafoil shape,equivalent stress,pressure contour,load and the spanwise length are obtained.By comparing and analyzing the calculation process and numerical results,the parachute-borne system produces displacement offset with wind direction,and under high wind speed and upwind conditions,the parafoil can open normally,while under the leeward and cross-wind conditions the instability will occur.Finally,the parafoil opening process controlled by mid-range closure is simulated.Damping control is used to simulate the closing rope,and the effect of closing control on the performance of parafoil opening process is studied.The changes of parafoil shape,dynamic load,spanwise length of opening parafoil,and width of cell are compared under four different conditions: series of closure and configuration of closure.The control law of load reduction and opening order of the closing mode is obtained,which provides some reference for the design and application of parafoil.