| With the development of aerospace industry,the spacecraft recovery in good weather conditions is carried out quite well.Because the hazard caused by the bad weather has not been assessed properly and completely,the spacecraft recovery is generally delayed or cancelled in bad weather environment until now.In order to master the impact of bad weather on recovery system and achieve the all-weather implementation of reentry capsule recovery,the raindrop distribution on canopy of parachute and fluid structure interaction(FSI)of parachute were studied numerically in this dissertation.The main contents in the dissertation are summarized as follows:The numerical simulation of rainfall environment was researched.The Euler-Lagrange two phase flow approach was employed to describe the relationship of airflow and raindrops.The airflow was treated as the continuum phase and the raindrops were treated as the discrete phase.In the discrete phase model the shape of raindrops was assumed to be spherical and some important parameters,such as the rainfall intensity,distribution of raindrop spectrum,and the terminal velocity of raindrops,were included.Various cases of rainfall environment were simulated via altering the values of raindrop diameters,the number of raindrops on the injection surface,the injection speed of raindrops relative to the airflow,and the mass flow rate.The raindrop distribution on canopy surface of hemispherical parachute in heavy rain was researched.The raindrop distribution was simulated numerically in many cases based on the assumption of whether the water film was formed or not on the canopy surface.Not considering the water film formation,the raindrops were trapped when they reached onto the canopy surface and the calculation of raindrop trajectories was terminated.When the water film formation was considered,the Lagrangian wall film model was added to simulate droplets colliding with canopy surface and water film movement forced by the airflow.The raindrop distribution on canopy surface of ringsail parachute in light rain was researched.Based on the configuration of the main parachute of Shenzhou spacecraft and the local rainfall characteristics of spacecraft landing zone,the raindrop distribution on the ringsail parachute canopy was numerically studied in the simulated light rain environment from the two aspects of forming water film and not forming water film.The unlike distribution characteristics caused by the structure difference of ringsail parachute and hemispherical parachute were analyzed.The fluid structure interaction of a ringsail parachute in terminal descent stage was researched.In the past years,the MpCCI(Mesh-based parallel Code Coupling Interface)has rarely been applied to study the FSI of parachute.The ringsail parachute FSI was studied using the MpCCI platform which was responsible for the data exchange between the nonlinear finite element analysis software Abaqus and the computational fluid dynamics software Fluent.The breath behavior of parachute in the descent process was simulated and the periodic variation characteristics of breath behavior were analyzed.The parachute breath process was investigated from the aspects of pressure and velocity distribution of flow field and canopy structure deformation.Besides,some inherent defects of MpCCI were solved by writing program.The performance of ringsail parachute FSI simulation in this dissertation verified the feasibility of applying the MpCCI platform into the research field of parachute FSI.In conclusion,the raindrop distribution characteristics on the canopy surface of hemispherical parachute and ringsail parachute were firstly researched in numerically simulated heavy rain and light rain,separately.Then,the ringsail parachute FSI was studied using MpCCI.The work in the dissertation can provide a certain reference value for the further research of parachute performance considering both the parachute FSI effects and rainfall environment. |
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