不同大气条件下超声速降落伞系统气动特性分析

Numerical Study on Aerodynamic Characteristic of Supersonic Parachute System under Different Atmospheric Conditions

火星探测任务中,超声速降落伞对于火星探测器的减速过程起着至关重要的作用。然而,火星探测器与超声速降落伞系统的数值模拟和风洞试验大多在地球环境中进行,不能完全复现火星用降落伞真实的工作环境,所得气动特性也与真实环境下火星降落伞气动特性存在误差。针对这一问题,文章开展了地球和火星大气环境下超声速降落伞系统的数值模拟研究,并分析不同大气环境、来流条件对降落伞系统气动性能的影响机理,以及不同探测器构型对降落伞系统阻力性能的影响。研究发现:相比于地球大气,在火星大气条件下探测器单体尾流颈部点更加靠近探测器,火星大气环境下伞体阻力略低于地球大气环境;随着截锥数量的增加,器前激波脱体距离、激波角度及颈部点至探测器间距均缩短,阻力系数增加;后截锥导致伞体阻力波动幅度增加,流动周期延长。随着来流马赫数的增大,伞体内压力波动增加,以致流场需要更长时间进入稳定的周期性变化;当来流迎角增大时,伞体内表面压力波动和流场周期性均减弱。此外,三维降落伞模型流场变化模式与二维模型一致,在周期内器前激波角度及脱体距离变化程度更为明显。

In the Mars exploration missions,supersonic parachute is always used for the aerodynamic deceleration during the decent and landing of Mars probe.However,most recent numerical and experimental studies are performed in the Earth atmosphere,which can not completely provide the real working environment and Martian atmosphere for aerodynamic characteristics of supersonic parachute.In this study,the numerical simulations of capsule-canopy system are conducted in Earth and Martian atmospheres,to investigate the effect of different atmosphere on aerodynamic performance of various capsule-canopy systems.As a result,compared with the results of Earth atmosphere,the neck point of wake comes closer to the capsule in Martian atmosphere,and the canopy drag in Martian atmosphere is slightly lower than that in Earth atmosphere.With the number increment of truncated cones,the stand-off distance of capsule shock,the capsule shock angle,and the distance of wake neck point from the capsule become smaller,and the canopy drag coefficient increases.The adding of truncated cones results in an increase in the fluctuation of canopy pressure and a prolonged period.With increasing the freestream Mach number,the pressure fluctuation inside the canopy increases,subsequently,it takes a longer time for the flow field around the parachute system to develop into a pulsation flow mode.As the freestream angle of attack(α)is increased,the pressure fluctuation on the inner surface of the canopy decreases,and the periodic change of the flow field decreases.In addition,the flow mode of the three-dimensional(3D)capsule-canopy system is identical to that of the two-dimensional(2D)model,however,the angle and stand-off distance of capsule shock fluctuate more obviously within a period.