Three Dimensional Simulation on Deformation of Jet Boundary in an Underexpanded Axisymmetric Jet

摘要

The jet boundary in a supersonic free jet issuing from a circular orifice deforms for Re* larger than several hundreds, where Re* is the Reynolds number at the orifice divided by the square root of the pressure ratio p0/p1 between the stagnation pressure and the circumference pressure. The phenomenon occurs by the Taylor-Goertler instability due to the curved jet boundary, in which a large velocity gradient exists. We have tried to simulate it numerically by a continuum calculation and the DSMC method. A general-purpose flow solver, CFD2000 developed by Adaptive Research, is used in the continuum calculation. In the DSMC simulation, the new intermolecular collision scheme is developed in order to compensate for coarseness of the cell-network. Petal patterns of the jet boundary are simulated by the continuum calculation. The number of the petals is 12 16, which is almost the same as that experimentally observed. The DSMC result also shows the deformation of the jet boundary, but due to the intrinsic and probabilistic fluctuation accompanying the method, the petal patterns are not positioned so neat as those by the continuum calculation.