Abstract:
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 temperature 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 that, 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.