Analysis of flowfield and surface heat flux uncertainties under typical blunt-body re-entry conditions
Uncertainty quantification (UQ) in the hypersonic flow regime offers valuable information to determine physical models in need of improvement and to assist in design of vehicles and flight experiments. Here we present results of UQ analysis based on the polynomial chaos expansion method to determine flowfield and surface heat flux uncertainty under typical blunt-body re-entry conditions. The NASA Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) code , was used for axisymmetric CFD calculations of chemically-reacting, hypersonic flow over the FIRE-II configuration. A third order polynomial chaos (PC) method using the Gauss-Hermite quadrature was applied for determining probability density functions and moments of output quantities. Input parameters such as freestream density, velocity, and temperature were varied, and the propagation of their corresponding uncertainties on output properties of interest through the flowfield was studied. The flowfield regions where the uncertainties are amplified due to non-linear effects have been determined. The most sensitive parameter to input variations was found to be freestream velocity. The surface heat flux uncertainty was amplified by more than a factor of five relative to the input velocity uncertainty of ±0.29%. Conversely, the freestream temperature has the least sensitivity. The utility of analyzing higher moments, such as skewness, in addition to mean and deviation of the uncertain output parameters has also been demonstrated. ^
Alina A. Alexeenko, Purdue University.