基于索膜有限元模型的翼伞气动变形仿真

Parafoil aerodynamic deformation simulation based on cable-membrane finite element model

对定常状况下翼伞的流固耦合变形问题进行了三维数值模拟。使用有限体积法计算了飞行时的气动载荷,分析了前缘切口和翼肋开孔对压强分布的影响;基于翼伞结构大位移小应变的特点建立了非线性索膜有限元模型,伞衣由不能承受弯矩的膜单元模拟,伞绳和切口加强带由只能单向拉伸受力的索单元模拟,仿真了受气动载荷后翼伞相对于理想设计位置的变形和应力分布。结果表明:该翼伞展长相对于设计值减小,"鼓包"形成后翼型最大厚度增大,伞衣变形后产生了额外的后掠角和攻角;最大等效应力主要集中在翼肋上的开孔和伞绳连接点处,需合理布置加强带以满足强度要求。

The fluid-structure coupling deformation of the parafoil was numerically simulated under steady condition. The finite volume method was used to compute the aerodynamic load,and the effect of leading-edge cut and ribs on the pressure distribution was analyzed simultaneously. Nonlinear cable-membrane finite element model was established based on the large displacement-small strain characteristics of parafoil structure.Canopy was modeled by membrane element which was unable to bear bending moment,and ropes and reinforcing tapes were modeled by cable element which could only bear uniaxial tension. The deformation relative to ideal configuration and stress distribution of parafoil were simulated on aerodynamic load. The results show that the span decreases compared with design value in flight,the maximum thickness of airfoil profile increases after bumps appear,and extra angle of attack and sweepback arise from canopy deformation; the maximum equivalent stress is mainly concentrated around holes and rope joints of ribs,and reinforcing tapes must be arranged properly in order to satisfy the strength requirements.