Research On Multibody Dynamics And Fluid-structure Interaction Of Parachute-body System

The parachute-body system is the main research object of parachute deceleration and recovery technology.With the fast development of aerospace and aeronautic technology,the emergency of many new kinds of aircraft and missions puts forward higher requirements for the functionality and suitability of parachute-body system.The typical working process of parachute-body system would experience flight,deployment,inflation,descent and landing stages,among of which the inflation step is a type of nonlinear fluid-structure interaction(FSI)problem and most complictated.Besides on,the dynamic characterisitcs of system are easily influenced by the parachute aerodynamics and structural deformation during flight process.Thus,it need to develop the simulation and experimental analysis of parachute-body system from the view of multidisciplinary coupling.This thesis focus on the numerical simulation and experimental investigation of FSI and multibody dynamic problems of parachute-body system during decelearting process,and the results attained are as followed.(1)The FSI technology of Arbitrary Lagrangian Eulerian(ALE)method is studied.The structure features of complex parachute and the parametric modeling technique of folded canopy for the simulation of parachute inflation are both expouned,the governing equations of parachute fabric structure and the surrounding incomprssible fluid are built and discretized by the ALE description.Aiming to control the over deformation of structural element,the mesh smoothing technique is introduced.a novel penalty coupling method adapted from the contact and impact technology is applied to constrain the node points between the structure and fluid elements.And the FSI computation of parachut inflation is implemented.(2)The numerical research of parachute finite mass inflation for low speed airdrop mission is studied.Addressing the ALE FSI technique and mesh moving strategy,the finite mass inflation of life-saving parachute is simulated and investgated.The inflation characteristics of parachute are comparatively analyzed with the test data from airdrop.The evolution mechanism of surrounding fluid and FSI characteristics are investigated,and the simulation results provid the theoretical basis and data support for the design and development of parachute,which has a strong performance of engineering application.(3)The supersonic inflation performance of Mars parachute is studied against the wind tunnel test data.Addressing the space-time conservation element and solution element(CE/SE)method and the mechanical dynamics solvers,the coupling platform for the supersonic parachute simulation is built.Taking the objects of full-scale and sub-scale model of disk-gap-band(DGB)parachute and probe system in Mars Science Laboratory plan,the simulation of infinite mass inflation for supersonic parachute system is implementated in the couping platform.The simulation results is validated by the NASA test data,the inflaion parameters and evolution of canopy shape are obtained,and the drag performance of Mars parachute is also analyzed.The influences of forbody on the fluid characteristics and distribution of bow shock near the canopy are visualized and studied comparing with the photos of the test.The simulation verifies the applicance of CE/SE-Mechanical coupling platform in the supersonic parachute FSI problem.(4)The injury probability of occupant under the opening overloads is predicted based on the multibody dynamic theory.Firstly,the flight dynamic models of life-saving parachut and occupant in the airdrop missions are built,then the ALE FSI method is utilized to simulate the opening overloads and tension curves of suspension lines for various conditions,and the trunk dummy model with the belt constraint system is built to analyze the impact of opening overloads on the human body.Finally,the injury index are summarized and the tolerace limited values of vulnerable parts are evaluated.(5)The dynamic similarity principle and sub-scale experiments of parachute-body multibody system in Mars exploration mission are studied.The related dimensionless parameters are defined,and the scaling parameters of earth and Mars flight test system are computed by the derivation of dynamic similarity principle of multibody system for the guidance of earth test design.The airdrop test is implementated by the airship platform,the trajectory parameters of parachute and load are obtained,the flight simulation and stability analysis of paracute-body system are by the dynamic model of steady descent stage and disturbance theory.The results show that the sub-scale test system can be used in the Mars exploration design and the dynamic models are also verifyed.(6)The integrated simulation of Mars Entry,Descet and Landing(EDL)process is studied.The seperated dynamic model of entry,deployment,inflation and steady descent stages of DGB parachute-lander system are built,the adaptive opening control method is developed to obtain the parameters of opening point,and the whole trajectory of EDL is asscoiated and simulated.At last,the multi-dynamic models of individual step is integrated and a multidisciplinary framework is built based on the object-oriented design language.The three-dimensional vision of parachute's opening process and lander's trajectory are implemented,which is an effective tool for the optimum design of system.This thesis focus on the related coupling dynamic problems of parachute-body system during the decerlerating process,the FSI method,multibody dynamic method and the integrated simulation techniques of paracute-body system are studied,and applied into the dynamic research and test design of parachute life-saving,Mars EDL.The research work in this thesis can greatly advance the development of parachute decelerating and recovery technology in the aerospace and aeronautic fields.