Deployment Dynamics Of Inflatable Membrane Space Structures Described By Absolute-Coordinate-Based Method And SPH Method

Large inflated space structures,such as inflatable deployable antenna,space habitation and inflatable supporting tube,are widely used in aerospace industry because of their light weight,small folded volume,low manufacture cost and high reliability.With the deployment of large space structures,inflate membrane space structure will undergo overall rigid motions,large elastic deformations and rigid(rigid-body motion)-flexible-gas coupled dynamics problem.Therefore the dynamics of inflatable structures is a multidisciplinary study.Combining the knowledge of the fluid dynamics and the structural dynamics,the purpose of this study is to model deployable space structures and predict the dynamics of the deployment process.Then the numerical results can provide the theoretical basis to design and optimize these structures.Previous studies have indicated that the Absolute Nodal Coordinate Formulation(ANCF)can accurately describe the coupled dynamics of the flexible structures with large rotations and large deformations.In this dissertation,the flexible components are described by the ANCF element and the constraints between these components are introduced in the system equation of the motion by the Lagrange multipliers.Besides,the implicit numerical integration algorithm is employed to solve the equation of motion established by the Lagrange equations of the first kind.However,there has been no report on combining ACB and SPH to research of the process of inflatable membrane structure.The major contributions of the dissertation can be summarized as follows.1.In this paper,the basic theory of Smooth Particle Hydrodynamics method(SPH)and the absolute coordinate method are introduced firstly.The Natural Coordinate Formulation(NCF)and Absolute Nodal Coordinate Formulation(ANCF)are used to model the rigid and flexible bodies,respectively.The Smoothed Particle Hydrodynamics(SPH)method is used to model the compressible fluid.For solid wall boundary conditions,the mirror particle method is used to reduce the near-boundary defects and prevent the non-physical penetration of the internal particles.For the flexible boundary,the virtual particles of SPH are embedded in membrane components contacted with the gas.And these virtual particles can also transfer interaction forces between the gas and the membrane structures.2.Based on the theory of weak gas-solid coupled,the Navier-Stokes equation and rigid-flexible system dynamics equation are solved alternately for the gas-solid coupling problems.In this study,the generalized alpha method is used to solve rigid-flexible system dynamics,and the second-order accuracy predictor-corrector scheme is used to solve the Navier-Stokes equation.3.Based on the proposed method above,A FORTRAN program is developed to study the gas-solid coupling dynamics problems including the gas compression in the cylinder,the inflation of the plane airbag and the expansion dynamics of the spiral membrane tube.The numerical results verify the feasibility and correctness of the proposed method.