Calibration of spalart-allmaras model for simulation of corner flow separation in linear compressor cascade

Abstract

This study focuses on the calibration of Spalart–Allmaras turbulence model parameters using the Bayesian inference approach to reproduce experimental measurements of corner flow separation in linear compressor cascade. The quantity of interest selected for the calibration process is the pitchwise distribution of Mach number in the wake of the linear compressor cascade. The model parameters are assumed to be random variables obeying uniform prior probability distributions. Sensitivity analysis is used to rank the importance and select the most influential turbulence model parameters for the calibration process. The sensitivity ranking indicates that two model parameters cb1 and κ are the most influential random variables resulting in a two–parameter Bayesian calibration process. The likelihood distribution is specified in the form of the Gauss distribution to include the experimental uncertainty. The likelihood distribution is used together with prior distribution to compute posterior probabilities of selected model para-meters. The polynomial chaos expansion is employed as a surrogate model to reduce the cost of posterior calculation. Numerical simulations with calibrated turbulence parameters show a significant increase in the accuracy of Mach number profile prediction for separated flows in linear compressor cascade. Numerical simulations also demonstrate that the calibrated set of model coefficients produce accurate predictions of the total pressure and Mach number profiles for the range of incidence angles that were not part of the calibration process.