球锥钝头体再入稀薄气体电离过程三维DSMC模拟与验证

Three dimensional DSMC simulation and validation of rarefied air ionization process for sphere-cone blunt body reentry

采用增大电子质量三个数量级并相应调整离子质量的方法,拓展化学反应的DSMC仿真方法处理稀薄气体电离过程;采用单温度模型处理全部化学反应,修正涉及电子的反应速率常数以保证真实化学反应速率;以直角/非结构网格相结合,运用碰撞网格自适应技术,基于MPI并行环境,开发适用于真实复杂外形的三维稀薄气体电离DSMC计算程序。对RAM-C II外形的再入绕流稀薄气体电子密度进行模拟验证,所得结果与飞行试验测量值吻合较好;对Stardust外形的再入稀薄段电离特性数值仿真分析,电子密度等值线云图与参考文献结果一致。相较于稀薄气体不含电离反应的DSMC方法,本文发展的模型和程序不会导致计算量的显著增大,可直接应用于三维复杂外形体极高速再入条件下的稀薄气体电离计算,为工程设计提供技术支持和指导作用。计算结果表明,极高速再入条件下传统稀薄流区的电子数密度足以引起通信黑障,需在通信设计上给予高度关注。

Based on the assumption that the electron mass is increased by three orders of magnitude and the ion mass is adjusted correspondingly,the traditional DSMC method for chemical reactions is extended for rarefied air ionization.Single tem perature model is used for full reactions,and the reaction rate coefficients involving electron are modified to guarantee the real chemical reaction rate.Combined with rectangle/unstructured hybrid grid,three dimensional rarefied air ionization DSMC program has been developed for real complex spacecraft configurations based on collision cell self-adaption and MPI parallel environment.Numerical test indicates th a t,the electron distribution obtained for RAM-C II case agrees well with flight experiment data,and the electron density contours completely match with those in references.Compared with the DSMC method for rarefied gas without ionization reaction,the developed model and program hardly bring significant increment of computing cost,it can be directly applied to rarefied air ionization simulation for the three dimensional complex geometries at extremely high reentry speed and provide technical support for spacecraft design.The computational results show that the electron number density during extremely high speed reentry process in traditional rarefied flow regime can be high enough to introduce communication blackout and some of attention should be paid in the communication design stage.