Uncertainty quantification analysis in hypersonic aerothermodynamics due to freestream

The CFD calculation is usually deterministic. However, errors and uncertainties always exist in the numerical simulation of complex engineering. Analysis and identification of source of uncertainty, and quantification of uncertainty play important roles in assessing the credibility of simulation results. Uncertainties are generally ubiquitous in highly complex aerospace systems. To obtain more reliable aerothermodynamics prediction, the uncertainty quantification and sensitivity analysis were carried out for the returning capsule hypersonic reentry flight. First, four uncertainty input variables (freestream velocity, freestream temperature, wall temperature and freestream density) were selected, whose variation ranges are ±120 m/s (±2%), ±10%, ±10% and ±10% respectively. And the samples were generated by Latin hypercube Design. Then, the thermochemical non-equilibrium numerical simulation method was used to calculate the aerodynamic heat. Finally, methods based on non-intrusive polynomial chaos(NIPC) and Sobol index were applied to uncertainty quantification and sensitivity analysis. The results show that the wall heat flux is not less than 15.9% under the given condition of uncertainty input variable uncertainty, and the peak value of the stagnation and shoulder are about 19.8% (0.087 MW/m²) and 17.3% (0.076 MW/m²) respectively. The uncertainty of heat flux is more sensitive to freestream density and velocity, and meanwhile freestream temperature and wall temperature variations almost have no impact on heat flux.