Flowfield Characteristics Under The Interaction Between The Inflatable Membrane Structure And Compressible Flow

Inflatable membrane structure is a kind of large deformable flexible structure. The interaction between the inflatable membrane structure and compressible flow can induce complex flow structures. This interaction exists extensively within the engineering applications. In this thesis, the Eulerian-Lagrangian method is used to study the inflation of cylindrical membrane and planar membranes. The flow field characteristics of the interaction between the inertial compressible flow and membrane are analysised. The flow field characteristics of the interaction between the external pressure waves and inflated cylindrical membrane are also studied. The results and conclusions are briefly described as follows:(1) The Eulerian-Lagrangian method is used to be the numerical method for studying the fluid-structure interaction of inflatable membrane structure. The 7th order WENO scheme based on characteristics splitting is used to solve the compressible flow governing equations. And the finite element method based is used to solve structural dynamic equations. The time difference scheme is the 4th order Runge-Kutta scheme. The block parallel method is used to improve computation efficiency for dealing with the complex fluid-structure interaction problems.(2) The cylindrical membrane inflation is studied. The flowfield characteristics under the interactions during the cylindrical membrane inflations are discussed. The results show that complex shock wave structures are formed in the inertial flowfield of the membrane during the inflation. The flow separation and deflection caused by shock waves then form large-scale vortex structures at two ends of the membrane. Based on the analysis of Lamb vector’s curl and divergence, it can be found that the vortex motion and momentum transportation are occurred mostly in the areas adjacent to the surface membrane and shock waves. Vortex motion in compressible flow leads to the appearance of bumps at two ends of the membrane and the instability of inflation. Furthermore, based on the dynamic force analysis, it can be found thatstress concentration and instability aggravate with the increasment of inlet pressure and velocity.(3) The influence on the planar membrane inflation of constraint conditions are studied. The compressible flowfield characteristics during the inflations are analyzed. The results show that the constraint conditions have little influence on the internal flow field of the membrane. The inflated shapes are significantly different at different constraint conditions. During the infalation, high pressure region is induced inside the membrane, and can lead to the dimple phenomenaappeared on top of the membrane. Through vortex dynamics analysis, it can be found that the vortex structures are mainly appeared in the area adjacent membrane surface. This corresponds to boundary constraints of the membrane. Therefore, shock structures do not appear during the inflation. In addition, the change of structural shap with iner pressure is got by the comparison study on form of the inflated plane membrane under different iner pressure, original shaps and constraint conditions.(4) The flowfield characteristics under the interactions between pressure waves in the external flow field and inflated cylindrical membrane are studied. The results show that during the interaction between incident shock and membrane, complex shock reflections are induced. There are Mach reflections appeared at the up and down sides of the membrane. Then the triple points and Mach stems are formed. By the influence of the Mach stems and high pressure gas, recompressed shock structures are formed behind the Mach stems. The diffracted Mach stems are intersected by each other behind the leeside of the membrane, and formed complex strong discontinuity structures. A depression appears on the windward face of the membrane subjected to the shocks and strong compression waves. This leads to the stress concentration. On this basis, the interactions in different flow field are numerically studied. Then, the influence of flow parameters on fluid-structure interaction and dynamic preformanc of cylindrical membrane is got.