The invention relates to a grid unit
particle number optimization method in rarefied
airflow numerical
simulation. The method comprises the following steps of: judging whether the number of simulationparticles in any
grid cell is within a set range or not in the numerical
simulation of the thin air flow by adopting a DSMC, and if the number of the
simulation particles is within the set range, notoptimizing the number of the particles in the
grid cell; if the number of the simulation particles exceeds the upper
limit value of the set range, repeatedly executing particle fusion operation according to a particle fusion criterion so as to enable the number of the simulation particles in each grid unit to be within the set range; and if the number of the simulation particles is lower than thelower
limit value of the set range, repeatedly executing
particle separation operation according to the
particle separation criterion, so that the number of the simulation particles in each grid unitis within the set range; and controlling the
particle number of each grid unit in the simulation domain, so that the simulation
particle number in each grid unit does not change greatly along with the
unit density and the
unit size, and the distribution of the simulation particles on different grid units is balanced.