Uncertainty Quantification of Vacuum Plume Simulations Using Direct Simulation Monte Carlo Method
CHEN Hao
1,LIN Zhen
2,LIU Cheng-cheng
1,ZHANG Bin
1,LIU Hong
1
Vacuum plume in real environment is uncertain whereas the numerical simulation is always deterministic, thus the influence of uncertainty on the vacuum plume is required to be elaborately studied. In this paper, the direct simulation Monte Carlo (DSMC) method was used to simulate the plume flowfield with various input uncertainties. Meanwhile, the probabilistic collocation method with sparse grid technique was used to describe the input uncertainties stemming from the incoming flow, wall condition and model parameters. The mean, variance and uncertainty of the output parameters, and the propagation of uncertainty were also calculated by the probabilistic collocation method. The corresponding results indicate that the uncertainties in flowfield sharply increase along the streamline when the flow speed reaches its maximum, and then decrease when close to the sound speed line. The influence of input uncertainty in wall temperature dominates in the downstream area of the sound speed line. Note that, the increment of uncertainty in the pressure is the most significant, which approximately equals to 2.1 times the input uncertainty (3.54%). In addition, the temperature jump uncertainty is almost constant, which is about 0.8 times the input uncertainty. This may be caused by the input uncertainty in the wall temperature that bounds the temperature jump uncertainty. As a consequence, the uncertainty in the heat flux (5.54%) is slightly smaller than that in the normal stress (6.25%), meanwhile the uncertainty in the shear stress (5.07%) is the smallest one. Finally, the Sobol’ global sensitivity analysis shows that the input velocity uncertainty and pressure uncertainty in the throat contribute the most to the uncertainty in aerodynamic characteristics, and considerably exceed the influence of the input uncertainties in the wall temperature and in the reference diameter of simulated particles.