前体尾流对降落伞工作性能的影响

为研究前体尾流对降落伞工作性能的非定常影响，基于Realizablek-ε湍流模型采用PISO算法开展了物伞系统的非定常绕流数值计算，获得了精细的流场旋涡结构。在此基础上，研究了不同拖曳比下物伞系统的尾涡演变规律、流场分布规律以及伞衣气动特性变化。结果表明:前体尾涡导致伞衣入口处的涡量大小和方向时刻变化，随拖曳比增加，涡量黏性耗散增强，进入伞衣的旋涡强度逐渐减弱，伞衣入口形成稳定的负涡量区，伞衣尾涡脱离周期随之延长；拖曳比对尾涡区后端（伞衣入口处）流场压力的影响远大于前端，随拖曳比增加，流动形式逐渐由闭式转变为开式，流场的速度分布和压力分布更为对称，伞衣入口形成稳定的正压区，内外压差增加；当拖曳比大于9时，前体尾流对降落伞阻力系数和表面压强系数的影响减小。 

Effects of capsule wake on parachute working performance

To study the unsteady effects of capsule wake on parachute aerodynamic performance, the Realizable k-ε turbulence model and PISO algorithm are used to calculate the unsteady flow around the capsule-parachute system, and an accurate flow field vortex structure is obtained. The research on the variation of vortex, the flow field distribution and the aerodynamic characteristics of the canopy at different trailing distances has been carried out. The results show that the vortex of capsule wake causes the magnitude and direction of the vorticity at the entrance of the canopy to change constantly. As the trailing distance increases, the vorticity magnitude gradually decreases because of the increase of the vorticity's viscous dissipation, and a stable negative vortex area is formed at the entrance of the canopy. The canopy vortex's escape period is extended. The trailing distance has a much greater influence on the flow field pressure at the entrance of the canopy than at capsule. As this distance increases, the flow form gradually changes from closed to open, the velocity and pressure distribution of the flow field become more symmetrical, and a stable positive pressure zone is formed. The internal and external pressure difference increases. The influence of the capsule wake on the drag coefficient and surface pressure coefficient of the canopy is reduced when drag ratio equals or greater than 9.