A parallelization strategy is applied to the Direct Simulation Mont Carlo (DSMC) method to improve its efficiency in non-equilibrium regimes. In order to distribute the workload among the processors, we decomposed the physical domain into the subdomains. The Message Passing Interface (MPI) library is used to transfer information between subdomains. We used an intelligent algorithm to specify the physical bounds of subdomains in an order to result in an equivalent computational time for each processor. The effects of domain splitting on the parallel speed up and the idling time of processors are studied. We then investigated a nano lid-driven cavity to investigate the effects of non-equilibrium on the rarefied flow behaviour. As the characteristic length of the driven cavity decreases nonequilibrium effects enlarges, which subsequently reduces the induced moment by the driven lid of the cavity. As a result the center of primary vortex moves toward the physical center of cavity geometry. It is seen that once the characteristic length of the cavity enters the nano scale the center of vortex location changes its trend and move away from the center of cavity. The Knudsen diffusion phenomenon which comes to the play when the frequency of molecule-surface collisions outweighs the intermolecular collision is hold responsible for this behavior.

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