DSMC developments since the publication of the book that would force changes to the discussions within the book.

• It is stated in the book that the DSMC method is restricted to dilute gases. F.J. Alexander, A.L. Garcia, and B.J. Alder (Phys. Rev. Lett. Vol. 74, p. 5212, 1995) have shown that relatively straightforward modifications to the method, that allow for the finite size of the molecules, cause it to reproduce the equation of state of dense gases.

• Improved procedures for dealing with the dissociation limit of the quantum vibration model were presented at the 20th Int. Symp. on RGD by R.G. Lord in a paper entitled "Modelling of dissociation of diatomic molecules using the Morse potential.

• Alexander, Garcia, and Alder have developed analytical expressions for the effect of rectangular cell size on the transport coefficients.

• The recent development of transient adaptive sub-cells (see Version 3 of the DS2G program) provides an efficient scheme for nearest-neighbour collisions and alters the recommended DSMC program structure. The effective cell size adjusts optimally to the local conditions and the user no longer has to choose sub-cell sizes.

• The next step towards relieving the user of the responsibility of setting all computational variables was to automatically set the time step. The conventional programs employ a single time step for the whole flowfield. The mean collision time can vary considerably, particularly on hypersonic flows, and keeping the time step small compared with the minimum mean collision time can involve a prohibitive computation time penalty. Procedures for variable time steps have now been developed. These are automatically set to a specified fraction of the local mean collision time.

• The new procedures have been implemented in a new general program DS2A. It is no longer feasible to index the molecules for collisions at each time step and "continuous bidirectional indexing" has been introduced. The time step for molecule entry is unrelated to the collision and move time steps and the program structure is radically different from earlier programs. Also the program can be compiled as a general program or as "intelligent" programs for particular classes of problems. These do not require the specification of any computational variables. To date, a "wind tunnel" option that produces the executale DSWT.EXE has been developed. This is restricted to (eventual) steady flows and the user specifies the working section size, the flow conditions and the model geometry. If there is insufficient memory for a good DSMC calculation, a warning is given and the program stops. These are intended for engineering calculations by inexperienced users and executable versions will be placed on the site in the near future.

Other sites dealing with recent DSMC developments and applications