Angular momentum conservative algorithm of collisional process in DSMC   method
  The traditional algorithm of collisional process in DSMC method, used for calculation of velocities of molecules after collision, is based on the conservation laws for linear momentum and total energy. This algorithm does not provide conservation of angular momentum with respect to some axis, but for non-rotating flow this circumstance is insignificant, since the mean value of angular momentum of such kind of flow is equal to zero. The situation changes for axisymmetric flow with rotation. In this case the traditional procedure leads to some internal source or sink of angular momentum that may distort the flowfield. In the paper the discussed effect is recognized and investigated. The angular momentum conservative (AMC) algorithm of collisional process is proposed. 
Petr A. Skovorodko