DSMC Calculation of Supersonic Free Jet through a Rectangular or a Multi-aperture Orifice by an Improved New Collision Scheme

A supersonic free jet through a rectangular orifice or a multi-aperture circular orifice that induces plume-plume interaction is investigated by the DSMC method with an improved new collision scheme. The new collision scheme suggested earlier conserves the total energy of each collision pair precisely during an intermolecular collision and the stability of the scheme improves furthermore. In order to apply the DSMC method to near continuum flow effectively, the time step should also be enlarged according to the cell dimension. A double sampling of molecular information is effective in the large time step simulation. It has been known experimentally that the core of the jet from a rectangular orifice expands strongly in the plane of the minor slot dimension and contracts in the plane of the major slot dimension. The expected 3-D structure of the flowfield with the rectangular orifice, the aspect ratio of which is eight, is reproduced in both planes by the DSMC method. Three-dimensional interacting flowfield in two parallel underexpanded jets is recalculated by the DSMC method using the new collision scheme.