Parallelization of direct simulation Monte Carlo code Pstc-2d

Pstc2d code which simulates the two-dimensional Rayleigh-Benard flow using the direct simulation Monte Carlo (DSMC) method has been parallelized on Intel Paragon XP/S15-256. The parallelization was carried out by employing message passing method. It has been made clear that parallelization efficiency is considerably worse when the number of processor elements becomes large. It is because the number of message passing increases in O(n2). A new algorithm which decreases the number of message to O(n) is proposed, and it gives a little affect on physical accuracy of calculated results. It was found that parallelization using the NX library is three times faster than parallelization using the PVM. Utilizing a large memory space of the Paragon, the Rayleigh-Benard system in the cavity of 44.8 mm in width and 5.6 mm in height with 1.28 million particles has been computed. The number of rolls agrees with that obtained by macroscopic hydrodynamic models. From this result, it is found that the DSMC method is applicable to simulate a continuum flow in a large scale system. (author)