| Summary: | 碩士 === 國立交通大學 === 機械工程系 === 90 === Flow fields of multiple underexpanded supersonic jets are simulated using the three-dimensional, parallel direct simulation Monte Carlo (DSMC) method employing an unstructured mesh incorporating static domain decomposition. One, two, three and four jets of argon gas issuing from the orifice(s) into a lower-pressure environment are considered, respectively. Inflow conditions at the orifice outlet (throat) required for the DSMC computation are calculated using the continuum approach. Ratio of upstream stagnation pressure to downstream chamber pressure remains fixed at 50 in the current study. Rarefaction parameter characterized by Knudsen numbers (based on throat conditions) is varied in the range of 0.001~0.1, which corresponds to the flow from near-continuum to transitional regimes. Results show that a distinct barrel shock and Mach disk structure is clearly captured for a single jet flow at Knudsen number of 0.001, while it is diminished to a purely compressible, expanding flow with increasing Knudsen number. Interaction between multiple jets is discussed in detail. Strong thermal non-equilibrium in translational degree of freedoms appears for both high and low Knudsen-number flows due to different reasons.
|
|---|
