Research On Folded Flexible Fabric Modeling Technology And Numerical Simulation Of Deployment Process

With the rapid development of materials science, the mechanical property of flexible inflatablefabric is greatly improved. And the flexible inflatable fabric has been widely used in aviation,aerospace, weapons and other fields with advantages like small folded volume, light weight and highefficiency. The fabric deployment process seems to be simple in principle, but actually it is a typicalFluid-Structure Interaction and nonlinear process. The deployment is the weakest and most dangerouspart in the entire work process of fabric, and the consequence of deployment failure is often severe.This paper mainly focuses on the flexible fabric folded modeling method, and the Fluid-StructureInteraction numerical simulation of folded fabric deployment process is conducted. The numericalresults are compared with tests results.Folding modeling is the first problem of inflatable fabric research. Complex folding model isdifficult to be created through current methods. Therefore two methods of reverse folding modelingmethods and realization of this modeling are proposed as: reverse folding modeling based ondynamics calculation and reverse folding modeling based on constraint deformation. These twomethods are utilized for folding modeling an airbag folded in a special way with complex shape, andthe inflation simulation is conducted to verify the feasibility and accuracy of this new modelingmethod. Folding modeling often cause errors, and the effect of traditional error correction technologybased on geometric principles is limited. An initial metric correction method based on finite elementtechnology is proposed. In this paper this correction method is utilized to achieve parachute folding inlatitude and longitude directions, and this method is also suitable for the correction of other foldingmodels. The feasibility and accuracy of this correction method is verified by comparison calculation.Based on the flexible fabric folding modeling and correction research, the arbitrary LagrangianEulerian (ALE) fluid-structure interaction model based on nonlinear finite element theory isestablished. The following work is conducted.(1) Under condition of infinite mass thethree-dimensional FSI research of parachute inflation process is conducted and abundant canopystructure and flow field information is obtained. By comparing the numerical results and test results,the parachute open laws under infinite mass condition are summed, and in particular case the"bottleneck" phenomenon emerges in inflation process.(2) Under condition of finite mass the canopystructure, flow field information and deceleration characteristics of U.S. C9parachute are obtainedthough FSI research in inflation process. By comparing the calculation results, tower test and airdrop test results, the parachute change laws of inflation to terminate descent process under finite masscondition are summed.(3) FSI simulations of inflation process are conducted for fabric with differentporosities, and the influence of fabric permeability in deceleration characteristics is studied.At last the CFD calculation of flow field around a porous canopy is conducted, the method ofreplacing traditional canopy wall boundary with porous domain greatly improve the calculationaccuracy.The study results are important to improve analysis level of understanding flexible inflatablefabric, especially parachute working mechanism.