Direct simulation monte carlo method: different way of reunion for decoupled processes

It is suggested in the present paper to reconsider the foundation of the molecular collision procedure in DSMC method by taking into account nature of gasdynamical measurements and by substitution the Khinchine limit theorem of queuing theory for the Kac model of recent substantiation of the Bird's algorithm. As a natural consequence of it one is led then to some corrections of this algorithm. First, the molecular selection procedure before their possible encounter proves to be changed to selection without replacement which avoids repeated collisions of the same particles during one time step and thus removes the most severe violation the particle dynamics in DSMC. Second, due to approximate stationarity of collision events for time step a trajectory correction for collided particles is introduced to recover joint development of the decoupled in DSMC molecular collisional and space motional processes. It maps the real time distribution for collisions of the first onto following time step of the latter. Practical significance of this correction is shown by simulation of a cavity problem.